racing in hot weather

Surviving in hot weather means adjusting the race plan. Here are some ways I've found to be pretty effective, especially geared towards endurance races (marathons/Ironman-distance triathlons):

1. Salt/electrolytes
2. Slow the pace
3. Liquid carbs
4. More water
5. Walk the aid stations
6. Wear a cap
7. Take ice if you're warming up
8. (Pre-race) Acclimate

Salt/electrolytes - a bunch of folks probably just need more of this. When it's warm and you're sweating more than you've been in training, you need to replenish much more. The on-course nutrition (i.e. Gatorade) is often an alright start, but can be a challenge to use right. It's all a bit personal, but for me it's got a lot of sugar and a strong flavor that kinda demands water after it, so you end up getting a lot of liquid in you and not enough nutrients. A next step could be to bring a bottle for the first part of the race. e.g. a dense electrolyte liquid mixer like Precision Hydration, or in tablet form (easier to carry in a pouch while you run) like SaltStick - which you can bring with you to the later miles if you really start to slow down. I also double or even triple-stack Nuun to get the electrolytes I need. Get the electrolytes in early, because it's hard to catch up once you've realized you've fallen behind. Bonus - the electrolytes help retain water, so it should help you pee less and you won't get hyponatremia. These are also great things to be considering in the lead-up (day before, race morning).

Slow the pace - lots of folks go in with a goal pace, but the heat has other plans. For example, the VDOT calculator has a feature that guesstimates a 4hr marathoner on a 96 degree day should expect to go about 4hr14m (assuming everything else goes smooth). It's not an exact science, but that's a roughly a 30 second per mile (!!) difference and with folks tending to go out fast early, there's a good chance that you'll tip into a zone you shouldn't be in and your body starts to overreact and burn deeper.

Liquid carbs - in general solid carbs are harder to get down on hotter days. Getting your stomach comfortable with taking both solid carbs (ie a bar) and the more liquid ones (gels) helps with changing weather conditions.

More water - drink some water, throw some on you. I feel like most people think to drink more in the heat though, so I wouldn't consider this novel advice. This also applies to the day before (and pair with electrolytes) and in the morning when you wake up/transit to the race, but make sure you'll have time to pee before you start.

Walk the aid stations - if you're already cruising out of control time-wise, just sacrifice the aid station running (if you haven't already). Walking for 50 meters won't materially effect your final time if you're bonking, but getting the right nutrition/ice/etc will absolutely help save you.

Wear a cap - it's hot and sunny! A lot of races don't have a ton of shade. A cap can help keep the heat off you and keep your body cooler for longer.

Take ice - on extra hot days, aid stations might have it. If they do, take some and throw a bit in your mouth or your cap or rub on your wrists. On the hottest days, it can help to cool the body down a little.

(Pre-race) Acclimate - get some runs in the heat leading up to the race. However, not always an option since we aren't weather wizards 😉. Not a doctor, but I enjoyed this in-depth article that talks about the many ways you can prepare your body for the high temps.