In New Genesis, the weather in the surrounding areas can change overtime. Certain enemies such as Alters can be enhanced by certain weather conditions.
Aelio's weather includes clear and cloudy skies, rain, and thunderstorms. During a thunderstorm, Gigantix Enemies can appear. Additionally, the PSE levels in all applicable PSE Burst regions will always be at a minimum of 4 levels during thunderstorms. This effect will not subside after completing a PSE Climax until the thunderstorm is over.