It's hot. HOT! And the National Weather Service has some great infographics to tell you all you need to know and expect.
Understand the difference between a Heat Advisory and Excessive Heat Warning. Neither is good, though.
I had Heat Exhaustion once. I was taking golf lessons and the heat got to me. I actually passed out for a couple of seconds. Scary! Being affected by the heat is no laughing matter. Treat it seriously!