Our Jackson is thriving in daytime temperatures between 70 and 75 degrees, with available cooler temperatures lower in the cage if possible. Ideal basking maximum probably shouldn't be higher than 82 (watch out for burns, depending on the bulb)
Is your cage mesh or screen? (glass enclosures are dangerous and can be the cause of many serious problems, such as overheating)
You may know this already, but until you post a DETAILED description, we won't know what you are doing (or not)
Does your chameleon stop gaping if you mist it?