battery light off and on!

What is your question?

I have had this checked out by Toyota dealership who said nothing was wrong. Another machanic said the same thing and I've had friends check the battery too. The car runs really fine. I've noticed this happens most often when it has rained or is raining. (when its very humid outside.) i replaced the battery and still does it !:( its bein the 3r time in 4 mounts now! is it the alternator or the cable battery or els? when i start the car the light goes off but when i star rolling it goes on. i had to clean the connector to the battery because there was a lot of corrosion. Now its all clean but still does it when its humid out! what can it be?? Anyone with any info/insight its greatly appreciate.