Wearing a single-breasted suit jacket flapping around unbuttoned, a shirt with its top button undone and no tie is not a good way to dress. Possible worse is walking about wearing your suit trousers and a shirt worn with top button undone. Now this is not because of some arcane rule, but simply because it looks indisputably ugly. Please note that office security badges are not an acceptable tie alternative.
Dressing for the sun is not tricky. The following are the acceptable modes:
- Suit buttoned up, shirt and tie, cotton hanky (for mopping brow), sunglasses (not wraparound).
- Shirt and tie, no jacket, trousers with belt (discrete buckle), shirt sleeves rolled up (works for the military, therefore OK for civvies).
- Shirt with two or three buttons undone (see your shirtmaker to get this right), no tie, no jacket, shirt sleeves rolled up (ditto trousers) and belt.
- Single-breasted suit with single button fastened, shirt with two or three buttons undone (but be warned, you may look a bit Euro).
Usual other combos of DB jackets and trousers, blazers etc also good, Lots of things work, in fact. Just don’t even think about taking off your tie and undoing your top button.
By the way, it’s not that hot. If you’re feeling the heat then get up earlier and walk more slowly. Or have an ice lolly.