In this kind of weather offices everywhere empty themselves onto any available green space ( or brown space, or even grey space ) at lunch time. Suit jackets get shrugged off, ties loosened, chicken wraps unwrapped.
I always envy people who get to wear smart clothes to work, although I know everyone who does would tell me I would hate it. To be certain that what you had on wouldn't be covered in paint, or plaster, ( or worse ) by the end of the day would be nice, just for once. I have never worn a tie to work in my life.