How to exercise safely during a heat wave - Wired

Humidity very much makes it feel warmer. And you can get to the point where generating enough speed to get air to move can generate enough heat to make it a horrible dance. Sometimes quitting is the best thing, and getting to air conditioning FAST.

I worked as a ‘facility technician’ for the department that ran the ‘physical plant’ of a ‘technology campus’, and monitoring everything and keeping the peps happy was literally a full time job. People might be surprised at the complexities of running heat and A/C systems at different times of the year, and what was going on in the environment. We’d run both A/C and heat to try to control humidity (try that in your car when the windows are fogging up). But low temp with high humidity was hard to deal with so many times. And in huge buildings, trying to control/effect that contained environment can be really near impossible. We caught so much hell at times because we weren’t omnipotent enough to control every component of the environment in all of the buildings across campus. We did do a pretty good job, but sometimes Mother Nature did it better. :man_shrugging:


Here in SoCal there is no humidity to speak of, so I don’t worry about it. Did get up early for a trail run this morning (2.5 hours). But started a road ride at 1:30 when my thermometer was reading 96° outside. I just stopped down the street from home to chug some ice tea, was well over 100° for most of the ride.

I also work outdoors in this, so its just not a thing. Before that I worked in a ships engine room where 130° was a cooler day (I’ve held a thermometer in my hand that read 192° before).

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Good for you. I was in Antigua, walking through Sr Nelson’s Dockyard, and it was in the 90’s, and really sunny. The small 4 masted schooner ran out of water, and by the time we got to the end of the break wall, we were suffering the heat. It was so dry, I wasn’t sweating at all. I was wearing my best Aussie Hat, and was basted in sunblock (sealing in the heat) and by the time we got back to the ship, I nearly passed out. I was dizzy as well as my wife. Thank Ford by that time the purser had found a pallet of bottled water, so was able to down one upright and feel better.

Yeah, no humidity can be worse than high humidity.

People need to be very careful during these days of nasty heat. Like it could even be sun exposure and not the heat itself that causes serious issues.

But I’m no expert. I’ve just been silly and ridiculous in hot and cold seasons. Somehow I survived.

Im in Houston and training for LoToJa in Sept (200 mi 1 day race). So i dont have the luxury of avoiding long rides in the summer. I am doing 100 mi rides nearly every saturday morning.

Heat adaptation is real. I was doing real well this summer until last week. I spent a week in Colorado and lost heat adaptation. I rode last sat and my HR was high even with lower power and didnt respond appropriately. My stomach struggled, etc.

We typically stop every 30 - 40 miles at gas stations, fill bottles with ice, drink an extra bottle of water or gatorade completely, sit in the beer cooler to cool the bodies, and continue on. We use tailwind with sis gels for fueling.


Central Texas here and I do a lot of 5-7 hour rides in the heat. June is typically not that hot (under 100f), but super humid. I try to get out the door between 5-6am, but it’s actually not that pleasant with temps around 80 and humidity in the high 90’s. By 10am, the humidity has dropping a bit and feels better even though temps are rising. July/August get hotter, but not as humid. My strategy is to keep intervals to around 10 minutes and provide some cool down time after each one. So, typically that is hill work.

I’ll have about 3.5liters of skratch to start with between a hydration pack and 2 bottles. Bottles will be empty pretty quick and I have some spots along the route where I’ll quickly hit drinking fountains to top them up with water to dump on myself as needed. I’ll do a store stop where I can get a coke and mix up some more skratch for the pack, but will do ice water in the bottles and keep dumping those on myself on climbs or really hot stretches. My new final treat (usually in the last 90 minutes or so after most climbing is done) is a quick stop at the 7-11 for a slurpee and to top off everything one more time with ice and water to get me home. I’ll try to get most of my hard work done before noon and get off the road by 1ish. I also make a habit of weighing myself before and after these rides to confirm I’m keeping up decently with hydration. I’m getting pretty heat adapted now, was able to knock out a couple 300+ tss rides this week with lots of climbing. And felt pretty good at the end of both rides and still able to make power.


Yeah I’ve found store stops for cooling liquids are a key component.

I actually saw someone get carted off in an ambulance last Sunday from heat stroke around noon. Heat index was around 115.

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[quote=“KorbenDallas, post:12, topic:94226, full:true”]
Phoenician here. 9am is the witching hour. I think the UV radiation is under talked about. Same temperature and humidity feel violently different under hazy vs cloudy skies. [/quote]

A few days ago I did a little experiment I’ve been meaning to do for awhile…checked the temp in the shade of a big oak tree in my hooded yard (and I used my body to keep any from filtering through leaves) vs direct sunlight. Was 90.1 F in the shade and 97.4 in the direct sun, with an instant read digital thermometer, and I was feeling the direct sun as I stood there waiting for it to stabilize (“feels like” was like 104F).

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It was 91 at around 6a in Las Vegas this morning! :flushed: :fire: :melting_face: That is way too hot for way too early.

I spent what seems like an eternity in government housing in North Carolina. I can remember nights where it was in the 90’s and 100’s and the humidity was somewhere close enough to 100% that the difference wasn’t meaningful. I had my first night terror during a night of ‘100/100’ when I got wrapped in the sheets when they were effectively glued to my sweat covered body, and my subconscious realized ‘I’M TRAPPED!!’ and hit the alarm. It was that year that apparently fighting the sheets caused me to fall out of the top bunk onto my head. Yeah, living there was so much fun…

Even in East Lansing at MSU, we had some really ‘North California weather’ at times, but it didn’t last as long as it did down there. I actually trained for a tour in a bit of it (in MI). That was not easy, as people are finding out. Tip: find a good sunscreen that won’t make you feel hotter, and try to wash it off at the end of the day so it doesn’t accumulate.

It’s interesting, having trained for the two extremes. I actually found it easy to ride in below zero temperature, and actually enjoyed it (but only pulled it off perfectly once). The key is knowing what to look out for, and not overdressing, which sounds like a contradiction. If you start sweating, you did something wrong and could lose the ride.



And don’t forget….


I’m lucky to have both a long paved path and a gravel route both with a lot of shade. But the humidity is still dreadful


Curious if anyone has a temperature or heat index cutoff they use for deciding to go or not. Currently waffling on doing a XC race this Sunday in North Carolina- I’d start at 11 AM with a predicted high in the mid-90s.

Living in Texas, we race with temps well into the triple digits. No cutoff temp for me, but forecast will certainly change the way I race and my hydration strategy. If gravel/XC race and starting before it’s too hot, I’ll make hay early and try to get up the course as far as possible before the heat gets oppressive. But at some point power output is affected and if often becomes a death march to the finish. Not my favorite brand of racing, but that’s the most effective approach I’ve used.


I rode in TX for a year and acclimated pretty well. Camelbak helps, I drank like a fish. But I never really got bogged down by the heat. Consistently being out there is all the matters. I never changed my routine nor felt substantial effects from the heat besides for one ride where I was pretty smashed and had to jump into every stream I passed by. Being young, lean and fit probably helped a lot tho. I think that article is obv aimed at the general population, not someone who considers their exercise as ‘training’ if you know what I mean

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Is 11am a normal start time for XC races?

I don’t know that I have a cutoff temp but I’d definitely have a strategy change regarding hydration and probably expect to be slower

Funny. “heat wave” is normal weather in FL…
I just go to the gym on the TM, or ride indoors… easy money,

It’s been a long time since I’ve done a USAC-sanctioned XC race but yeah, there’s usually waves throughout the morning. This series does cat 1 at 9 AM, cat 2 at 11 and cat 3 at 1:30. For the past several years I’ve done more of the marathon races which tend to start earlier. Figured I’d give these a shot to remember how to race XC before trying to upgrade/qualify for nationals next year.

Ah okay. I thought it might be some sort of wave thing

A lot of great suggestions here! We have discussed some of these ideas, and the science behind some of them on the podcast. If you’re interested, you can check out that conversation here:

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