It’s been a few years now that I have been thinking about the climate and its effects on health. I had as a starting point the climate of the city I have grown up and lived in (Naples, Italy), and over the years I noticed different physiological patterns with the seasons, affecting mood, energy levels, fatigue, skin, libido, etc.
I think there are some objective parameters determining good and bad climates, though there’s also a range for personal preference and individual adaptations. Generally speaking, I have found that sunny, dry and cool climates are best for health as well as for physical beauty.Mexico city
I think that the amount of sunshine hours, latitude, humidity, rainfall, average temperatures in each part of the day are factors worth considering.
Sunshine, Darkness, Daylight, & Seasons
The amount of sunshine in a given place is one of the most important factors to take into account. Bright light, including sunlight, increases pregnenolone-progesterone-DHEA-testosterone production, from cholesterol, by activating/repairing the cytochrome oxidase enzyme. Sunny weather promotes energy levels and metabolism, even without direct exposure; it helps keep the blood sugar up and the cells in the stable, high-energy state, rather than the unproperly excited one. The light, orange and red wavelengths present in the sunlight spectrum seem to be responsible for that. Since red light penetrates the tissues, direct exposure provides useful energy and CO2. For the other effects of direct sunlight and vitamin D levels, I have outlined them in the light article, because I felt it was off topic here, and more appropriate there.
People seem to be healthier when it’s consistently sunny; germs are quickly killed by exposure to sunlight, especially at high altitude, so sunny climates more often get a natural disinfecting action on surfaces. There’s no doubt that a sunny climate is a good starting point (but we will see how too dry environments are bad for the health). Many North Americans and Europeans are shocked by the sometimes serious lack of sunlight at high latitudes in the winter, so they spend time or move to places with a lower latitude, where more sunlight is guaranteed in the winter (the lack of sunlight, at high latitudes, is coupled with the short-day stress). Too cold temperatures are negative in themselves, too, because our tissues produce inflammatory cytokines when they are chilled.
Darkness, especially when prolonged and consistent, seriously affects the hormones; it lowers blood glucose, increasing cortisol, adrenalin, and free radical damage. It damages mitochondria, and it’s likely that stress that causes thyroid function to decrease in the winter. In northern regions, most people gain fat during the winter. The needs for thyroid and vitamin D also increase greatly in the winter. The effects of the season, though, decreases as the latitude gets lower.
The long summer days are restorative, winters are destructive. At sunny low latitudes, the bad effects of the northern winters are reduced, but so are the good effects of the very long summer days. Whales learned that it’s good to change hemispheres with the seasons. Migrating cyclically can be good, for example when living in a northern region spending the winter in a sunnier, low latitude location would mitigate the harmful effects of the winter. At the tropics, low latitude locations, days are close to 12 hours all year, so I think it would be good to have some northern summer days. The combination of low latitude and moderate or high altitude in some countries means that there are regions with a good climate all year round while still getting the benefits of living at high altitude.
Steroid production increases in the spring and mitochondria are more stable. Many people notice a sharp increase in their libido in spring, but the full repair of the winter-darkness damage reaches its peak at the end of the summer. The peak of the darkness related damage, which is cumulative, reaches its peak about a month after the shortest day of the year.
A good climate ensures enough sunshine, especially if it avoids too dark winters.
The Importance of Rain
I became interested in the phenomenon of people feeling euphoric when the weather gets rainy; in places like Mexico, or in dry hot weather in general, it’s often a matter of settling the toxic dust that blows up in dry hot spells, but a bigger, more general contribution might come from an effect of negative air ionization. Some research in Poland suggests that negative air ions increase the lungs’ ability to destroy serotonin, which could account for their benefits. 
During the dry season in Mexico, there can be weeks without rains, and I have found the inflammation to increase when the drought was prolonged. In a dry period, the dust becomes a big problem in the city deserts, and a very important function of rainfall is to clean the air. The city or town air contains various harmful materials, from natural but mostly man-made causes; fecal matter, silica, polycyclic aromatic hydrocarbons (from smokes), lead, manganese, silver, various other metals are present in nanoparticles and since they’re much smaller than cells, they freely enter it, causing inflammation. 
People have found to feel better after a rain, and to enjoy the fresh clean air following it, especially in areas in which rains are infrequent in certain seasons, for example in southern California or in central of Mexico.
Knowing this, in terms of liveability I think a climate that isn’t prone and usual to too long dry periods is preferable, especially if there are polluters in the given place. Since even cars are enough to harmfully pollute the air, I can’t think of many places that are free of polluters today.
Humidity, Health, & Physical Beauty
I’ve been wondering, for a time, why summers in Naples, Italy, were so unpleasant and why that weather would discourage activity. The reason was the combination of high temperatures and high humidity.
When both high temperatures and high humidity are present, the metabolic rate tends to decrease. This happens to allow physical activity when heat dissipation is limited (high humidity prevents proper dissipation), and the resulting decreased oxidative metabolism is inflammatory.
It’s the combination of high humidity with high temperature that’s the problem. When the humidity is high, warm temperatures start becoming unpleasant, but with low humidity, I think the body can adapt to average highs of up to 32°. It seems that high temperatures and high humidity aren’t compatible with high metabolic energy and high exploratory energy.
“I’ve spent a few months in Florida and Veracruz, and could hardly function. When I was teaching at the University in Jalapa, students said “you shouldn’t expect us to work much, we’re tropical people.” In Florida, old hypothyroid people like it, it substitutes for metabolism. If you don’t wear clothes, and have water to dip into occasionally, it’s tolerable.” Ray Peat, PhD
“Yes, I think it’s mainly the sense of confinement . In a bad climate, such as Florida, there’s a similar feeling of imprisonment, even if it’s a big house in a pretty setting.” Ray Peat, PhD
However, there’s more to it than that. Besides preventing over-heat during activity, humidity seems to solve many other problems and support health in other ways. It inhibits the growth of mites and fungi (including molds), and so can reduce allergies and asthma. I have noticed some allergies to go away immediately when I switch from high to low humidity, some allergies and symptoms go away, for example I have experienced it with mold allergy.
Too low humidity, on the other hand, has known harmful effects. It damages respiratory mucous membranes, predisposing them to dehydration and infections.  A moderate amount of humidity seems to be important for skin health, too. Heating the indoor air usually creates very low relative humidity, exposing people to the same risk of very dry weather, even more.
Over the last couple of years, having experienced living in a country that has both dry and humid areas, I started observing differences in the physical appearance of people as the humidity changed. Specifically, I found women in dry, cool areas to be more attractive than those in those in humid ones, especially when warm and humid. I’m not sure what goes on, or if it’s a personal preference of mine, but moderately low humidity, besides being healthful, seem to have an important effect on physical beauty.
Wind & Urban Heat Islands
The wind from the ocean or sea (when it’s big enough) prevents extreme temperatures. Because the drift of the winds is usually from southwest, it’s preferable to stay on the west side of the continents, to be on the upwind (windward). That has an effect on climate, as well as on air pollution. The weather satellites can give an impression of the movement; the website windy.com is what I used. This is valid from small towns to continents. In a city or a town, the upwind (west, southwest) edge will usually be the one with the least smokes and other air pollutants, because the wind most often blows them all the way to the opposite side. When a place is on the west coast of a continent, the air coming from the ocean or sea is cleaner than when it has passed through industrial farm country and various other polluters (cars, factories, etc.). I could imagine it as combing a dandruffy head, and be on the side the comb starts from, rather than where it ends at.
An important liveability problem of today’s cities and towns everywhere is represented by the so-called “urban heat islands“. Deforestation, replacing trees with bare ground (cement, asphalt, etc.), causes the microclimate to change, making daytime temperatures raising much more and quicker. Moderate humidity can help keep some areas pleasant in spite of that, but even in central Mexico, where humidity is generally moderate, I have found the daytime temperatures to rise too much for my comfort in urban areas. Many middle-aged and old people who live in some of those places have noticed the sharp change, in just a few decades (population in Mexico tripled since the 1960s, with a peak of breeding in the 1970s and 1980s). Going just a few miles away from a city, in the woods, (especially on the west side, where the wind usually comes from), will make a noticeable change–getting away from the urban heat island. Even in Valle De Bravo, Mexico, a fairly small town, I could notice a difference in the microclimate between the central square and the woodsy areas on the edge. Climatologists have found relevant differences between the city centers and the edges.
“Inside a city, away from trees, the daytime temperature rises very quickly; on the edge, on the upwind (windward) side without the smoke, the air is best.” Raymond Peat, PhD
“…even a small area that’s densely wooded has a better microclimate. Very dry air can irritate the respiratory membranes, and seems to make them more susceptible to infections.” Raymond Peat, PhD
“Yes, the seasons have changed [In California and Southern Oregon], with rain being less regular and so less useful, more destructive. The same thing has happened in Mexico, and is continuing everywhere. It’s the obvious driver of climate change. There’s a good Ted talk by Allan Savory on preventing desertification. The new government of Mexico is budgeting for the organized planting of millions of acres of trees.” Ray Peat, PhD
“Yes, good climate [1940s’ California], people swimming and fishing in the San Diego river. The water table in our well was just a few feet below the surface, fruit trees and alfalfa pasture thrived without irrigation. Streetcars made it easy to travel. Millions of people with lawns, brought in for the war industry, and the substitution of freeways for trolleys and trains, changed it completely.
Suddenly in the late ‘40s things started drying up, including 100-year-old trees. L.A. drained Owens Valley for their water, destroyed the farms there.” Ray Peat, PhD
Real World Climates
In the United States, I think the best climates are found on the west coast. The breeze from the ocean moderate temperatures and the continental influence of a big dry area ensures moderate humidity. The coast is long, so there’s a range of climates. The range of good coastal climate seems to roughly go from Santa Barbara, CA to Brookings, OR. Right on the coast, with moderate temperatures, the humidity isn’t much of a problem. Personally, I would prefer a more restricted range that would ensure more regular rains, and cooler temperatures, for example starting from Monterey, CA instead of Santa Barbara, since the latter is more likely to experience rainless periods (we’ve discussed, in terms of liveability, the problem of prolonged lack of rain). The strong oceanic breeze seems to affect the climate to up a few tens of miles inland.
Nice, lower humidity climates are found more inland, but anything in California more than a few tens of miles seems to be too hot, at least in the summer. Southern Oregon has generally good climates, for example Grants Pass, Ashland, and Medford, but the winter nights can get too cold, probably because of the altitude. Summers and other seasons seem good. Eugene has nice spring and summer weather, but too dark and rainy in the winter.
“I lived in Grants Pass and went to school in Ashland, and some summers worked in the woods outside Medford; I thought the climate in that area was generally pleasant, less rain, and sunnier than Eugene. ” Ray Peat, PhD
“Yes, [Eugene] very comfortable weather most of the time through September.” Ray Peat, PhD
The United States has some high areas that have good weather in the summer, maybe in spring too. From Santa Fe, NM to Boulder, CO, there’s a range of climates at high altitude, healthful by itself. The summers are very sunny, cool, and dry, so it would be convenient to spend a few weeks to get the benefits of the altitude, while enjoying the nice weather. Denver, Boulder, Glenwood Springs, and Leadville, CO, are some examples of high altitude locations in the US with good weather in the summer. Leadville isn’t that viable as a first choice as it’s extremely high, so it requires proper adaptation to moderate altitude before going. It would require moving from location to location at increasingly higher altitude, with a few days spent in each place of increasing altitude. I wrote more thoroughly about altitude adaptation in a specific article. Santa Fe, NM and nearby towns are other locations with similar characteristics. Fall and winter, though, are too cold in these places, so they aren’t optimal for all season comfort.
In Europe, Spain and Croatia have interesting climates. The area of Santiago de Compostela, Galicia, and the area of Cadiz, Andalucia, in Spain, are similar to some of the climates of the US west coast. Huelva, Andalucia, is a reasonable climate, with cool winters and dry warm summers (I discovered that chemical factories’ pollution is a big problem there). In Croatia, the coastal area, for example from Rijeka to Split, seems too good to be true; it has everthing I would expect from a good climate: moderate humidity, moderate temperatures, sunshine, very regular rains even in the summer.
When considering a place in the tropics or subtropics, altitude and humidity must be taken into account. Moderate or high altitude, desirable by itself, also has the benefit of mitigating the high temperatures at these low-latitude, tropical or equatorial places. Below 1500 meters is usually considered a moderate altitude, though in the context of its effects on health I would consider anything below 2000m to be moderate, and anything above 2000m I consider high altitude. At low latitude, it’s possible to have at the same time altitude and all season comfort.
For example, there is a strip of land across southwestern and central Mexico, from Guadalajara or Tuxpan, Jalisco, Zamora or Morelia, Michoacan, Guanajuato, San Juan del Rio and Acambaro, to Zitacuaro, Valle de Bravo and Cuernavaca, which has reliably a good climate and moderate altitude (1550-2000m/5,000-6,500 feet roughly). Some of the towns at higher altitude, e.g. Toluca and the nearby towns (Calimaya, Almoloya de Juarez), Pachuca, etc. are always cold at night, but the days are always comfortable. Mexico City generally has a good climate as well, but the pollution and the urban heat island effect are extreme.
Since I don’t know the climates of all parts of the world, there will be more, but those are the ones I’m aware of, or have tried personally. There are no high altitudes in continental Europe or the US with good climate year round, because the latitude isn’t low enough. So, on a yearly basis, one has to choose between the benefits of altitude, including longevity, and seasonal comfort. In the US there are some places at moderate or high altitude which have very good weather in the summer.
It’s good to keep in mind that the climate one lives in affects health, in some cases quite profoundly. Some climates or weather patterns can inhibit recovery from hypothyroidism and fatigue among other syndromes.
Negative air ions are created when an electron–a tiny particle with a negative charge–piggybacks onto a big molecule of oxygen. The molecule of oxygen, which has no charge before this event, then carries a negative charge. The oxygen continues to carry a negative charge if microscopic drops of water surround it and its visitor, preventing the electron from leaving.
At Niagara Falls, beaches, and tropical rain forests, as well as anywhere there is a storm, the moisture in the air tends to keep an extra electron on zillions of oxygen molecules. These charged oxygen molecules turn into the equivalent of miniature vacuum cleaners by attracting dust, smoke, pollen, mold spores, and other unwanted particles which have positive charges, since negative particles attract positive particles. When the charged oxygen molecules attracts positive particles, they form heavy clumps, which drop to the ground, leaving the air we breathe fresher and cleaner.
Negative air ions occur far more often in nature than in our homes and buildings, where heating systems and air conditioners remove moisture from the air, making it hard for electrons to stick to oxygen molecules. People can buy ionizing air cleaners to reverse this problem, but need to be sure the machines are powerful enough to have an effect, since often only industrial-strength ionizers are effective.
Perhaps more important, negative air ions can relieve depression and enhance sleep quality if used properly as a treatment for these problems. For example, an experiment at Columbia University found that the mood and sleeping problems of people who received high-density negative air ions improved just as much as they did in people who received bright light therapy, a treatment that had already been proven effective.
What remains a mystery about negative ions, however, is how they work. Scientists suspect the effects may be linked to the ease with which ionized air moves from the lungs throughout the body, improving circulation.
2. Environ Health Perspect. 2016 Mar; 124(3): 306–312.
Traffic-Related Air Pollution and Dementia Incidence in Northern Sweden: A Longitudinal Study
Anna Oudin,1 Bertil Forsberg,1,† Annelie Nordin Adolfsson,2 Nina Lind,3 Lars Modig,1 Maria Nordin,3 Steven Nordin,3 Rolf Adolfsson,2 and Lars-Göran Nilsson4,5
Exposure to ambient air pollution is suspected to cause cognitive effects, but a prospective cohort is needed to study exposure to air pollution at the home address and the incidence of dementia.
We aimed to assess the association between long-term exposure to traffic-related air pollution and dementia incidence in a major city in northern Sweden.
Data on dementia incidence over a 15-year period were obtained from the longitudinal Betula study. Traffic air pollution exposure was assessed using a land-use regression model with a spatial resolution of 50 m × 50 m. Annual mean nitrogen oxide levels at the residential address of the participants at baseline (the start of follow-up) were used as markers for long-term exposure to air pollution.
Out of 1,806 participants at baseline, 191 were diagnosed with Alzheimer’s disease during follow-up, and 111 were diagnosed with vascular dementia. Participants in the group with the highest exposure were more likely than those in the group with the lowest exposure to be diagnosed with dementia (Alzheimer’s disease or vascular dementia), with a hazard ratio (HR) of 1.43 (95% CI: 0.998, 2.05 for the highest vs. the lowest quartile). The estimates were similar for Alzheimer’s disease (HR 1.38) and vascular dementia (HR 1.47). The HR for dementia associated with the third quartile versus the lowest quartile was 1.48 (95% CI: 1.03, 2.11). A subanalysis that excluded a younger sample that had been retested after only 5 years of follow-up suggested stronger associations with exposure than were present in the full cohort (HR = 1.71; 95% CI: 1.08, 2.73 for the highest vs. the lowest quartile).
If the associations we observed are causal, then air pollution from traffic might be an important risk factor for vascular dementia and Alzheimer’s disease.
Oudin A, Forsberg B, Nordin Adolfsson A, Lind N, Modig L, Nordin M, Nordin S, Adolfsson R, Nilsson LG. 2016. Traffic-related air pollution and dementia incidence in northern Sweden: a longitudinal study. Environ Health Perspect 124:306–312; http://dx.doi.org/10.1289/ehp.1408322
3. Toxicology in Vitro
Volume 29, Issue 1, February 2015, Pages 195-203
￼Influence of physicochemical properties of silver nanoparticles on mast cell activation and degranulation
Silver nanoparticles (AgNPs) are increasingly being incorporated into products for their antimicrobial properties. This has resulted in increased human exposures and the possibility of adverse health effects. Mast cells orchestrate allergic immune responses through degranulation and release of pre-formed mediators. Little data exists on understanding interactions of AgNPs with mast cells and the properties that influence activation and degranulation. Using bone marrow-derived mast cells and AgNPs of varying physicochemical properties we tested the hypothesis that AgNP physicochemical properties influence mast cell degranulation and osteopontin production. AgNPs evaluated included spherical 20 nm and 110 nm suspended in either polyvinylpyrrolidone (PVP) or citrate, Ag plates suspended in PVP of diameters between 40–60 nm or 100–130 nm, and Ag nanowires suspended in PVP with thicknesses <100 nm and length up to 2 μm. Mast cell responses were found to be dependent on the physicochemical properties of the AgNP. Further, we determined a role for scavenger receptor B1 in AgNP-induced mast cell responses. Mast cell degranulation was not dependent on AgNP dissolution but was prevented by tyrosine kinase inhibitor pretreatment. This study suggests that exposure to AgNPs may elicit adverse mast cell responses that could contribute to the initiation or exacerbation of allergic disease.
6. Int. J. Mol. Sci. 2018, 19(1), 246; doi:10.3390/ijms19010246
4. Synergistic Effect of Metal Oxide Nanoparticles on Cell Viability and Activation of MAP Kinases and NFκB
Ángela Dávila-Grana, Lara Diego-González, África González-Fernández and Rosana Simón-Vázquez *
Inmunología, Centro de Investigaciones Biomédicas (CINBIO), Centro Singular de Investigación de Galicia, Instituto de Investigación Sanitaria Galicia Sur (IIS-GS), Universidade de Vigo, Campus Universitario de Vigo, 36310 Pontevedra, Spain
In recent years, there has been an increase in the production of several types of nanoparticles (Nps) for different purposes. Several studies have been performed to analyse the toxicity induced by some of these individual Nps, but data are scarce on the potential hazards or beneficial effects induced by a range of nanomaterials in the same environment. The purpose of the study described here was to evaluate the toxicological effects induced by in vitro exposure of human cells to ZnO Nps in combination with different concentrations of other metal oxide Nps (Al2O3, CeO2, TiO2 and Y2O3). The results indicate that the presence of these Nps has synergistic or antagonistic effects on the cell death induced by ZnO Nps, with a quite marked beneficial effect observed when high concentrations of Nps were tested. Moreover, analysis by Western blot of the main components of the intracellular activation routes (MAPKs and NFκB) again showed that the presence of other Nps can affect cell activation. In conclusion, the presence of several Nps in the same environment modifies the functional activity of one individual Np. Further studies are required in order to elucidate the effects induced by combinations of nanomaterials.
Cold temperature and low humidity are associated with increased occurrence of respiratory tract infections
The association between cold exposure and acute respiratory tract infections (RTIs) has remained unclear. The study examined whether the development of RTIs is potentiated by cold exposure and lowered humidity in a northern population.
A population study where diagnosed RTI episodes, outdoor temperature and humidity among conscripts (n = 892) were analysed.
Altogether 643 RTI episodes were diagnosed during the follow-up period. Five hundred and ninety-five episodes were upper (URTI) and 87 lower (LRTI) RTIs. The mean average daily temperature preceding any RTIs was −3.7 ± 10.6; for URTI and LRTI they were −4.1 ± 10.6 °C and −1.1 ± 10.0 °C, respectively. Temperature was associated with common cold (p = 0.017), pharyngitis (p = 0.011) and LRTI (p = 0.048). Absolute humidity was associated with URTI (p < 0.001). A 1 °C decrease in temperature increased the estimated risk for URTI by 4.3% (p < 0.0001), for common cold by 2.1% (p = 0.004), for pharyngitis by 2.8% (p = 0.019) and for LRTI by 2.1% (p = 0.039). A decrease of 1 g/m−3 in absolute humidity increased the estimated risk for URTI by 10.0% (p < 0.001) and for pharyngitis by 10.8% (p = 0.023). The average outdoor temperature decreased during the preceding three days of the onset of any RTIs, URTI, LRTI or common cold. The temperature for the preceding 14 days also showed a linear decrease for any RTI, URTI or common cold. Absolute humidity decreased linearly during the preceding three days before the onset of common cold, and during the preceding 14 days for all RTIs, common cold and LRTI.
Cold temperature and low humidity were associated with increased occurrence of RTIs, and a decrease in temperature and humidity preceded the onset of the infections.
Influenza and humidity – Why a bit more damp may be good for you!
Influenza viruses cause much winter-time morbidity and death in temperate regions. We still do not understand why ‘flu is more common in winter. Since the 1960s, investigators have studied the role of relative humidity and temperature on viral survival, transmission and infection rates but results have demonstrated only inconclusive trends. Over the past few years however, a series of exciting studies have instead focussed on absolute humidity and demonstrated highly significant correlations with viral survival and transmission rates in both laboratory and epidemiological models. Here we review the evidence for a causal association between absolute humidity and ‘flu transmission and outline how this could lead to a new approach to curbing this and perhaps other viral epidemics in the winter months.