My workplace every year is like an oven all summer and a freezer all winter. In the winter the trick is layers upon layers, normally I'll throw a long sleeve ts under a shirt under a large work ts and if needs be a hoody over the top if I have to. Our heating/AC at work is craptacular. Seriously in 5 years it's never worked.

In summer our approach is less clothing and plenty of water. I find drinking ice cold water on a boiling hot day isn't that great because the initial reaction of "hmm cold!" is offset by the fact that the coldness can cause your stomach to cramp (causing you to have the trouts)