How big is your tank and how much water do you have in it? From what you said, it sounds like you have a smaller tank (10, 20 gallons?) with relatively little water in it in if the light is heating the water that much. If you do, adding more water (and a bigger tank) would help keep the temp from climbing as much or as quickly.
If you do have a higher water level, what wattage is the light, and how hot is it making the basking area?
If the basking area temp is OK with the light, you could try what I've been doing to help lower the water temp when it gets too warm: I've started filling some of the small plastic bottles from mineral water you can buy (Aquafina, Poland Springs, etc.) and freezing them. Then just add them to the tank to lower the temp.
It's good to check the temp with a thermometer, especially if you have a smaller tank.
"You become responsible, forever, for what you have tamed." -Antoine de Saint Exupery-