 Now, the Department of Housing and Urban Development defined what it means by extreme heat event. It says that's a period of severe heat and humidity with temperatures 90 degrees or more for at least two to three days. But local agencies can use their own definition of what will trigger these payments. Now, HUD officials say this is going to let people use AC when they need it without risking heat-related illness, knowing they don't have to worry about cutting back on food or medicine in order to just stay cool.