Location of hamster:
Change the location of the burrow where you keep your hamster. This could be a cage, a glass aquarium or any other place you keep them in. Relocate to a dark and cool side of the house. If you have a basement or garage, it is going to make a good enough difference for the hamster. Even if you are keeping them in a room, keep them away from window sills and areas of direct sunlight. Do remember that closed containers and glass aquariums where you keep hamsters lead to humidity and a rise in temperature.
The place that you keep the pet in should be properly ventilated. Circulation of fresh air helps in dissipating heat and prevents humidity from building up. You can get a fan installed in the room. However, make sure that it is not exactly above the head of the pet. A rotating fan is much better.
Cool water is the best gift that you can give your pet during the heat. Make sure that he has plenty of cool water to drink at all times. Apart from the drinking water, you can also use water to cool his cage. Cool a bottle in the freezer. Wrap it in a towel and keep it next to his cage or cot. The cold water will keep the temperature down and provide a cooler medium. You can use two bottles, one in the fridge and the other next to the hamster so that you can rotate when the water gets warm.