sitting outside 35C in the shade, looking over the ionian sea bottle of cold sauvignon blanc and a plate of even colder seafood trumps a cold rainy day and a cuppa soup. :-)
It varies. In today's air conditioned offices there is a lack of heat rather than excess, so the appetite isn't reduced. But when I used to take a break on the Med (not done so for years) I found the excess heat upped my consumption of fluids but meant I only wanted something small if anything at all, to eat mid-day. A reasonable breakfast in the relative cool of the morning, and a decent meal in the evening, was enough.
Although it is 37º here I will still cook a curry or s/s chicken with all trimmings, (never a roast) but family come home and say "can't it that, too hot, want a sandwich" well I do not like sandwiches or salads.