Drink water - lots of water. Eight 8 oz glasses of water a day - at least.
Your body is mostly water. If you end up in a deficit, heat sickness or heat stroke may ensue.
Drink room temperature water to be able to drink more and absorb more. Here’s a website that explains different situations in which you should drink water at different temperatures.
http://www.healthyandnaturalworld.com/drinking-cold-or-warm-water/
If you feel thirsty, you’re already at a deficit and needs to be corrected ASAP.
Make sure kids are drinking water and staying hydrated. And your pets too!
Temperature Reference
Water freezes at 32o F (0o F)
Refrigerated water is between 35-45o F (1-7o F)
Room temperature is between 68-78o F (20-25 o F)
Body temperature is 98.6o F (37o F)
Your hot water heater is probably set somewhere between 110-140o F (43-60o F)
Water boils at 212o F (100o F)