Hot, Humid and Cold Weather

Hi all,
This summer is my first hot humid summer with my Gen III. Mileage went down from 47-48 per gallon to 42-43. Been running AC a lot as well. At first, I was in a panic as I only have 26,000 miles on my car. But after reading some threads, it appears that the optimum operating outside weather/temp is 80 degrees, low humidity and not running the AC. Also, in the winter, my mileage drops to 42-43 per gallon. Here in So Cal we are experiencing nearly 80 percent humidity at times during the day with temperatures over 98 degrees (not normal for us) and the thick, moist air seems to have an effect on air/gas ratios. Just a heads up for us all to remember.