Derived from the word Yeat (a rapper) combining W and Yeat, its is used to describe when Yeat goes crazy in a song, also commonly used is streamers chats when reacting to Yeat.
guy: hey, do you listen to sweater weather?
girl: yeah, are you coming out to me in any way what-so-ever?
guy: still questioning.
girl: well, I support you :)
Cold (often windy) but sunny weather that looks extremely pleasant through the window when one is inside, but is in fact quite uncomfortable to be outside in.
origin: An Icelandic expression: "Gluggaveður" (literally: Window-weather).
A-"have you looked outside? what a nice day we're having!"
B-"This looks like window weather to me. You should bring a jacket."