Adult Panther Chameleons are relatively hardy and can withstand a wide fluctuation in temperatures as long as the temperature extremes are not prolonged. 

However, they should be most comfortable during the day at slightly warmer temperatures than what humans would enjoy, any where in the low to mid 80's.  The cage should have temperature gradients to allow the Panthers to thermal regulate themselves for optimal health (eg. 90-95 degrees near the basking light to 70-75 degrees near the cooler, bottom area of the cage). 

During the night, they should also experience a drop in temperature of approximately 10 degrees to allow their metabolism to slow down.  During the winter months, you can lower the ambient temperatures by a few degrees and decrease their feeding frequency slightly. 

Babies are very susceptible to high temperatures and care must be taken not to over heat them.  If anything, too cool is better than too warm as far as babies are concerned. 

As previously mentioned, rainfall amounts vary significantly depending on what part of Madagascar you are in with the Western region being wetter than the Eastern areas.  I'm sure Nosy Bes and Ambanjas (Western locals) enjoy more humidity than Sambavas and Tamataves (Eastern locals). Because of my location in inland Southern California, the winter humidity can be very low but I have not had any difficulty due to the dryness, even with my Western area Panthers.  I try to mist my animals at least twice per day.  Babies again are more susceptible to dryness and they should be misted about 3 times per day if possible.  However, the cage should have the chance to dry out inbetween mistings to curtail bacteria growth in the wetness.