its even possible to sync the weather depending on "zones". take f.ex the mt chiliad. you could change each players weather to 8 (rain/storm) for those players who arrives there, and make sunny weather everywhere else. it works perfect
keep in mind that the weather needs a whole (real) minute (== 1 game hour) to change, so if a player drives through an area, he maybe wont notice the change. and smooth weather changes needs the regular game clock enabled...