It depends on just how high your ambient temperatures get and how long they stay high. You can take some fairly easy and inexpensive steps to cool off your snakes without resorting to air conditioning, unless of course you're looking for an excuse to install it.
Some options:
- Replace the warm water in the water bowls with cooler fresh tap water. That will help remove heat in the tubs, or the snakes can wrap around the bowls if they want to cool off.
- Place some plastic bottles filled 2/3 of the way with water on their sides in the freezer overnight. During the hottest part of the day put the bottles in the snake room in front of the rack, and set up a fan to blow air across the bottles so the cooled air hits the racks.
- Install tinted window film designed for the exterior of your windows on the south side of the house; the kind that goes on the inside of the windows doesn't work nearly as well, which is why it's cheap. Last spring I installed BDF EXS15 mirrored exterior window film on my south and west facing windows and noticed a substantial difference in my electric bill and with how warm those rooms got during the day.
- It's a longer-term solution but if you can plant shrubs or trees that will eventually grow up to shade your south and west-facing windows during the summer months that will also help keep the house cooler.