I'm surprised no one suggested "What funny weather!" for the OP in 2007 or "What a funny choice!" in May 2010.
Very good point."funny" doesn't always mean amusing but can also mean strange! The dubbers usually translate it as "buffo" even where the situation is deadly serious.
Agree, I' d write What sh...y weather ! (What lousy weather !)I would most likely expect "The weather sucks!" or "This weather sucks!" (slightly different but perhaps closer to the Italian exclamatory sentence)
One could of course also say "What *** weather!" with an ample choice of adjectives that we use when we don't like the weather : crappy, nasty, horrible etc.