I was emailing with a fellow runner in Charlotte earlier today and happened to mention that I went for a run at 9:30 this morning and it was already unbearably hot/sticky/miserable.

“I don’t know how you did it at 9:30!,” she wrote back. “I ran this morning at 5:30 and it was already 80 degrees!”

Who’s crazier — the person who slept in and ran at 9:30 or the one who went out at 5:30 when it was five degrees cooler — is open for debate. What’s not debatable is how crazy it is to workout in weather like this and not hydrate. Some quick reminders to get you through the next couple of teetering-on-100 days, thanks to the folks at the University of Tennessee at Chattanooga.

How much do I need to drink? Sweating is a very personal thing, you may go out at 9:30, run four miles and break a mild glow, I’ll go out and look like one of those kiddie pool water fountains, spraying every which way. Here’s how to calculate your personal sweat rate: Get naked and weigh yourself. Then get dressed and workout for half an hour, not drinking anything or going to the bathroom. Then get naked again and weigh yourself. The amount less you weigh is the amount of water you’ve lost, and thus how much you should be taking in to prevent said loss. So if you lost a pound, you should drink 16 ounces of fluid during that half hour workout.

Start out well hydrated. And don’t just gulp down a glass of water right before heading out. Start hydrating the evening before.

Don’t wait until you’re thirsty to drink. The “thirst mechanism” isn’t triggered until you’re 2 percent dehydrated.

Drink throughout your workout. Say you’re that person above who lost a pound during the half-hour workout. Take your water bottle with 16 ounces and sip at it throughout your workout.

Drink cool fluids. There’s no greater deterrent for drinking than to take in a long tug on your Camelbak only to get a mouthful of water suitable for brewing. Toss an ice cube or two into your water, or freeze a half full water bottle overnight and top it off before heading out.
The final arbitur. As always, the litmus test for weather you’re drinking enough is the color of your urine: the less yellow the better.
Drink up afterward. According to UT Chattanooga, the 30 minutes immediately after a workout is crucial to rehydrating.