When you're asleep, you can't actively combat the heat. You also probably have a tough time getting to sleep when you're overheating as it is. There are plenty of ways to stay cool at night so you can sleep comfortably despite the heat. For example, you can build your own air conditioner (or use an alternative method), get a cooling pillow like the Chillow, and put your sheets in the fridge before bedtime. Trial and error will decide which methods work best for you, but all will get you closer to a cool night's rest.