I heard an opinion that physical activity in temps over ~98F, a normal human body temperature, is not safe, since your body's ability to dissipate excess heat on its own becomes severely limited, and you need to drink LOTS of liquids to aid your body. You really have to be on top of this to avoid heat stroke. I did commute in temps over 100F but I wouldn't go on a longer ride when it's that hot. I drank two full bottles of water during those days. I normally don't even drink one bottle in temps below 90F.
Originally Posted by
jeffpoulin
It depends on the humidity as much as the absolute temperature. When sweating is no longer sufficient to maintain one's body temperature, it's too hot. That can be 95 degrees with 95% humidity, or 115 degrees with 5% humidity. Personally, I draw the line around 95 degrees F, unless it's really humid, then it's more like 85 degrees.
Although, I noticed that in NYC the humidity would drop significantly when temperatures cross over 100F. Those dry 105F days seem to be easier to deal with than 95F/95% days.
Originally Posted by
Chris Pringle
It's amazing how the body adapts with proper training and nutrition.
I think it's more about YOU knowing how to deal with it than your body actually adapting to it. I've seen people faint on bike rides in much lower temperatures because they had no idea how to deal with the heat and simply didn't drink enough water.