An Etymological Dictionary of the German Language/Wetter
Wetter, n., ‘weather, storm, tempest,’ from the equiv. MidHG. wëter, OHG. wëtar, n.; corresponding to OSax. wëdar, ‘weather, tempest, storm,’ Du. weder, weêr, AS. wëder, E. weather, and the equiv. OIc. veðr (Goth. *widra- is wanting). If Teut. wedro- is based on pre-Teut. wedhro-, OSlov. vedro, n., ‘fair weather’ (vedrŭ, ‘bright, clear’), is related to it. It is possible, though less probable, that wetró- is the Aryan base, with which also OSlov. větrŭ, ‘air, wind’ (from the root wê, ‘to blow’), coincides. —