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The Dangers of Wet and Dry Heat

High temperatures can be dangerous regardless of where you are. The dangers are two-fold; dehydration and the loss of electrolytes, mostly sodium and potassium, through sweating. However, the dangers aren’t quite the same if you are in an area with very high humidity as they are if you are in a place with very low humidity.

The body’s normal response to the heat that approaches or exceeds body temperature is to sweat. This is increased if a person is doing something active because they are generating additional body heat. Sweating causes dehydration. Sweat also contains both sodium and potassium, and if either of these becomes depleted, a person can suffer heat exhaustion or heat stroke. These two chemicals are exceedingly important for regulating body temperature. 

If they become unbalanced, the body temperature can soar rapidly, which is the heat stroke or heat exhaustion. This is why the military gives soldiers salt pills if they are deployed in a hot region.

All of this is true whether you are in a high humidity or low humidity environment. So what is the difference and which is more dangerous?

The difference is sweat.

In high humidity areas, where the humidity is above 80%, the sweat doesn’t evaporate very quickly because the air is already filled with moisture. It tends to be the most uncomfortable because the sweat just rolls down your body, leaving you sticky and wet. However, profuse sweating is an obvious cue that you should drink fluids with electrolytes added. People who are even mildly observant should know that they need to rehydrate when they are dripping large amounts of sweat.

A strange thing happens when the humidity drops below 15%, though. People sweat just as much as under high humidity conditions, however, the air is so dry that the sweat evaporates the moment it gets to the surface of the skin. Even people who are quite observant may never realize that they are sweating, dehydrating, and losing electrolytes. There are literally no visible signs of it.

By the time a person starts feeling the first effects, usually dizziness, it can already be too late, if they are somewhere where they can’t rehydrate and take electrolytes. This makes dry heat substantially more dangerous than wet heat. 

In dry areas, and this includes Montana in the summertime, the only thing that can be done is to drink fluids and take electrolytes even if you don’t feel like you need either. If you don’t, you could pass out and die without ever knowing that there was a problem in the first place.


What do you think?

13 Points

Written by Rex Trulove


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    • It is important to health and it can be easy to forget. Around here, I have to get myself in the habit of drinking water with a tiny amount of sodium chloride and potassium chloride added, or sports drinks, even when I’m not thirsty. That is especially true when I’m working on the Church flower beds. Most of the work is done in the sunshine and noise laws say that I can’t mow or weed-eat until at least 9 am. That gives me an hour before the heat kicks in. It takes about 3 hours to do it all, so I start drinking the fluids before I even start.

      Waiting until you feel thirsty is a very unwise mistake.

    • Very true. We have very low humidity around here in the mid to late summer. That is the time that coincides and contributes to forest fire season. Firefighters absolutely must keep themselves hydrated because working on a fire makes dehydration about twice as bad. Our temperatures may be in the-mid 90s with a humidity of 12%, but working on a fire, the men and women can experience temperatures well over 100 and with the same low humidity. They are working hard, on top of that. It isn’t uncommon for firefighters to collapse and need to be taken to the hospital for emergency rehydration.

      When our humidity drops below 15%, about 80% of the procedures done at the local hospital are for dehydration.

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