give me tips how to stay cool at work in a 100 degree weather

So I work at an elementary school as a yard duty supervisor so we’re basically outside the entire time watching kids at recess times and when we start work in August it’s gonna be 100° still 😓so how can I avoid being hot ? What can i wear for sun protection and to stay hydrated? Is there things i can buy? I dont wanna get sunburnt again because i already did when i went to the waterpark 2 weeeks ago and it hurt me soooo bad!