See people moan about people moaning when warmer weather hits the UK, but I think its completely justified.
1) Our houses / buildings are designed to keep in heat and not be drafty, effectively the opposite of warmer countries (can you imagine a house in the UK furnished internally with cold marble/tiles etc. it'd be freezing in the winter!)
2) Our life-style is based around the weather being cold/unobtrusive and us wanting to be in doors. Sure it's really good to get a BBQ out in this weather and dust off the garden furniture, but its something different for us, we don't do it often and we certainly don't get to do it in our workplace.
3) Many work-places in the UK aren't air conditioned. Can you imagine walking into an office somewhere in Spain (for example) that didnt have air-con? Even the cheapest of hotels in the Costa Del Sol are air conditioned!
4) Our pace of life doesn't suit hot weather. We work all day with very few breaks. There's a reason many hot countries have the equivalent of a Siesta. Also, watch the way people move generally, those used to a hot climate move more slowly in everything they do.
5) Our hot weather is rubbish. When I was in Spain a few months back it hit 34 degrees one day in the sun. But it was lovely, the humidity was low, I wasn't rushing to be anywhere or do anything and all my clothes were correct for hat type of weather, plus anywhere I was out had been designed so shade was available.
We are (normally) a small island with a settled climate that isn't extreme in any way, we get rain and cold weather (but not too cold), that is what we design our lives around, we don;t design it around near on 30 degrees with 80-90% humidity. People are right to moan!