Green’s Dictionary of Slang

(Aus.) angry.

1895		Coburg Leader (Vic.) 5 Oct. 4/2: A.S. was wet because O.S. would not take her home.
1907		Brisbane Courier 29 May 6/3: No, they weren’t wet (angry); it was just for fun.
1941		Howard ‘Heat’ in Mann Coast to Coast 124: Got you wet, haven’t they?
1959		G. Slatter Gun in My Hand 213: Don’t be wet. Up them. We don’t want trouble with the bloody johns.