So I am very hardy person. Ideally I'd wear shorts and linen shirt anywhere close to 20C (68F?). Many other people aren't going shorts unless over at least 27C (80F).
The environment is always business casual or semi formal, so there is no real need to be wearing full suit, but still as one an only guy in shorts you stand out.
So the most obvious question is, should I always wear trousers unless majority wear shorts? Or is it acceptable?