How hot is too hot to run?

The hottest I ever ran was when it was 122 degrees. Once when it was 120, I jumped into my pool fully clothed, put on my running shoes, and went for a run. Before a quarter mile my hair was completely dry, and my shirt was almost dry.

Upper 70s

That's 50C. Sounds dangerous.

Worst I've ever felt from heat was when I got locked/shut in a toilet at Tombs of the Kings in Cyprus. The door had an odd mechanism and jammed. F**k I thought I was going to die in there at one point. I even tried kicking the door through. Finally got out. My friend would've noticed I was 'missing' so it probably would've been OK, but even so.

Running in 45C isn't something I want to repeat either.

If you go on google maps and look up the usage stats for the track in Doha, one of the most popular times is 12am-3am. I don't know how they train in that climate. It's the desert. Never really should've been a city there.

I bet they light the track. Can you imagine a track in Texas or Florida having lights on so people can train at night? It seems absurd to think that could happen in the US. But ya, given the choice, I'd rather just not live in a place it gets to 120F

I lived in Phoenix for five years. Because the humidity is so low 110F was fine. Houston though with much higher humidity might be intolerable at 90F. The challenge with Phoenix was remembering to drink fluids because you don’t realize your sweating buckets

Back in high school I'd run at noon every day. I remember one week I ran 10 miles a day at 110-115 degrees. I went on to win a national title that year.

I don't have much to add to this discussion, except that--as I've posted in one or two other annual early summer Heat Sucks threads--there's research making clear that age decreases our ability to shed heat. This explains why, after living and running in Mississippi for the past 24 years, I'm having a tougher time at age 68 than I've ever had. At first I thought it was all in my head, because I never really minded the heat. One summer Sunday morning about 20 years ago I went out and ran 17 miles through the hills with no water, and didn't feel all that bad. Now that same run would strike me as a potentially fatal excursion.

Heat alone is merely one fact; heat, humidity, and radiant sun work together to burden your heat-shedding systems. I think we tend to discount the radiant sun aspect too quickly, but it's amazing how much more quickly you start overheating at a given heat & humidity when the sun is on you. And again, this all becomes more obvious, which is to say more depressingly real, as you age. Something happens after the age of 60.

Summer AM runs in North Mississippi start to become oppressive in mid-June and that lasts into mid-August, when the humidity slowly ebbs. The actual AM temps aren't that bad. Get out on the roads by 6:30 and, when the humidity is up, you may get 76 degrees with 98% humidity. It's the humidity and corresponding dew point that gets to you, not the temperature per se. 75 and dry is delightful. 75 and muggy is....harder. And the moment that sun comes up, you're screwed. I used to start two hour runs at 6:30 and around 8:15 it felt like I was hitting triple witching hour, where temps were rising, humidity hadn't fallen that much, and then the sun just whalloped you.

I try to get out on the roads by 6. Some people around here get out by 5:30, at first light. That's probably the way to go.