Luckily Summer is almost over so you shouldn't have to deal with the heat too much until next summer. But here are some ways of keeping safe in the heat.
Drink Plenty Of Water
It's important to stay well hydrated in the summer heat. You should drink plenty of water, and drink water even if you don't feel thirsty.
If you can, also soak a bandana in water or even your hat it helps to cool you off.
Take As Many Breaks As You Can.
Taking Frequent breaks is important, in the heat of summer you can get heat stroke and can die from it.
Don't overwork yourself. I'd rather tell my boss off if he didn't allow me breaks in the summer heat.