First introduced as suffering from amnesia, Weather aided Jolyne at Emporio's request. Distant and a little naive, he continues to assist Jolyne and her companions from there after.
Personality:
When deprived from his memories, Weather was mellow and eccentric. He would boldly stand a few inches next to Jolyne's face to get her attention rather than call her name. He was trustworthy and compassionate, rescuing those in need without caring for his own safety. Unless someone he knew was in danger, Weather hardly panicked.
Stand:
Weather Report ("Weather Forecast" in the dub): a versatile Stand that has control over weather. His Stand is usually in a cloud humanoid shape. His Stand can quickly formulate these vapors to stop or distort his enemies' attacks. He can also use his Stand to bring otherwise unlikely elements of the weather to rain down on enemies.
(Source: Wikipedia, edited)