i noticed you don't mention what your cool side's temp is, or how you take the temps... so although i have no additional info other than what has already been offered to you... i thought i'd pull this info from our caresheets for ya:

TEMPERATURE
~90F (warm side)
~80F (cool side)
75 or below is unhealthy
Maintaining proper temperatures is essential to keeping your ball python healthy – failure to do so can lead to a host of issues from poor feeding to potentially lethal respiratory infections. For this reason you want to make sure you are able to measure the temperatures accurately. The sticker-type label thermometers sometimes seen used on aquariums are not sufficient for measuring much more than the temperature of the surface they are stuck to and many of the dial-type analog thermometers available in pet stores are routinely inaccurate. Do yourself and your ball python a tremendous favor and invest in a digital thermometer – one of the most cost-effective and easily available is the Accu-Rite digital thermometer/hygrometer combo available at large stores such as Wal-Mart. These retail for appx $15 and include a probe making it possible to monitor the warm side and cool side temps as well as the humidity levels all simultaneously. You can also invest in a temp-gun for appx $25 which uses a beam to give you instant surface temperature readings (note – these cannot measure air or ambient temperature however).


HEAT SOURCES
Heating pads designed for human use have been used with great success by a large number of keepers – but it must be noted that you must obtain one which does not have the “auto-shutoff” feature or you will be unable to maintain your temperatures. These are usually available in large stores and pharmacies for appx $10 and the same caveats for UTH apply – make sure you have some clearance under your enclosure.

MONITOR YOUR TEMPERATURES – If the ambient room temperatures in your house fluctuate then likely the temperatures in your reptiles enclosures are as well. If you find it difficult to maintain your temperatures adequately you should invest in a thermostat to help regulate your temperatures and keep your reptiles healthy.

Heat lamps make decent supplemental heating sources but when using this approach be aware that light-based heat can contribute to the quicker evaporation of moisture in the air of your enclosure. Unsuitably dry conditions can leading to difficult sheds and other health issues. When using this method to supplement heat make sure visible light sources are not left on 24hrs – this constant light can cause great stress in these creatures. Non visible heat lamps (red or black bulbs) should be utilized if the source must be kept on overnight.