You can go outside for about 30 minutes at a time but try and stay under the shade if possible.
If you stay outside longer than that try and spray yourself down with a water hose. You can also get those moist rags that you freeze and wrap around your neck to keep you cool.
But if you don't have to be outside then it's best to try and stay inside near air conditioning as much as possible until late evening.
If you have some light work to do outside then try and do it early in the morning or late evening while it's cool outside.