Let us starting with what can be put to the category “old wives tales”. I am sure many of you will have heard somebody talking about the weather affecting their “rheumatics” or “arthritis“. People living in cold and damp conditions are worse affected.
So how can forthcoming bad weather cause sudden pain to shot through your hand, down your arm, up your neck, or across any other parts of your body? Medical science is now looking at ‘rheumatoid arthritis‘ as an autoimmune disease. This on the one hand makes it even more bizarre that the weather could affect your immune system in some way. But the common experience tells you that people are more susceptible to ailments in the winter months.
It is the health static that more people visit their GPs during these months and more death occurs at this time of year, particularly in the very young and elderly. Our immune system is at a developing stage through our early years and works less efficiently when we are older.
The GPs will tell the people that it can give some relief from symptoms. You heard of retired people spending the entire winter months in the Mediterranean and some even relocated completely to a warmer and drier climate. Some medical studies have been undertaken but no actual mechanism or clinical factor between damp conditions and rheumatics has been founds.
On warm summer days you can see the steam billowing from the towers and then it disappears as the water vapour evaporates into the surrounding atmosphere. A different sight is seen on damp days and especially on damp, cold winter days, the steam still below out but instead of disappearing it usually heads eastwards and out over the valley.
There is one situation where there direct causal link between health and humidity. In hot humid climate people need to be aware of its affects. Not only in this situation do we have a direct link to health but we can use our new knowledge to gain an understanding of the problem. The situation results in ‘heat exhaustion‘ due the human body overheating.
As warm-blooded mammals, we have to regulate our body temperature within quite narrow limits. Most people generally know that this is around 37°C. you also will have heard ‘hypothermia‘ where the body temperature drops by more than a few degrees and progressively shut down organs to maintain supply of blood to the brain for as long as possible. When body temperature is raised by a few degrees, this causes stress on our respiratory system and is particularly dangerous as the onset of effects are more sudden and can quickly lead to fatalities in people with heart conditions.

respiratory system

Perspiration is our in-built system for cooling down. This relies on water vapour in our sweat evaporating from the skin. A problem arises at high relative humidity where the ERH of our seat is lower than the relative humidity of the surrounding air, as we have in humid climate. In this situation no water vapour evaporates and therefore no cooling takes place. We do of course keep sweating more and more as our body attempts to cool itself and maintain ‘homeostasis’ due to our in-built thermostat.


The ERH of pure water is 100% which means there is no relative humidity below saturation where water ill not evaporate. We don’t sweat pure water because if we did we would soon dehydrate as our body pumped out sweat to replace the loss through evaporation. Our sweat contains salt and this lower the ERH to about 75% if it was simply pure water and salt. This means that if the surrounding air has relative humidity above 75%, water will not evaporate from our sweat. As the surrounding temperature increases the relative humidity drops and when we got hot and sweaty the water in our sweat will evaporate off into the air because it has lower relative humidity than the ERH of our sweat. In the humid climate where the relative humidity is high this mechanism for cooling our body cannot function efficiently as water vapour will note move from our sweat to the surrounding air with a higher relative humidity than the ERH.
As long as you stay in the hot the humid conditions will of course keep you sweating and the sweat will run off or soak into your cloths. Losing sweat this way does not cool you because the evaporation will not occurring and all that happens is you stay hot and become dehydrate. Unless you do something to cool yourself and replace the water loss, the consequence will be heat exhaustion. 

hot day  

check my lost post Hurricanes, typhoons and cyclones




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