Warm weather making AEGs shoot slightly hotter? Sure, when compared to freezing weather.
Temperature will affect FPS on an AEG, but it has nothing to do with warm weather. Cold weather (read: freezing) will lead to FPS decrease, from the rubber components (especially the hopup sleeve) becoming rigid and degrading the air seal.
But there should be no difference between warm weather and hot weather. This is the first time I've heard anyone suggest otherwise.
"The Bird of Hermes is My Name, Eating My Wings to Make Me Tame."