I live in the Denver area. The summers are pretty nice. It can get hot sometimes: 105F was this year's record in Denver, and we had about 5-10 100+ days, but mostly in the 90s in July/August. However, the low humidity (8-20% typically) makes the heat bearable. And I think this summer was a bit above average. I didn't think it would, but it seriously makes a huge difference. The winters are great too.. especially if you enjoy winter sports and can handle mildly cold weather (it doesn't usually drop below 5F except in the Rockies).
Personally I'd prefer to live in a slightly colder climate: one that didn't have 90+ degree days. San Francisco's climate is nice. Unfortunately it's a bit far from mountains for my taste. But I'd still live there.
As for everything else:
Anywhere in the midwest: bitter cold (colder than Denver & less snow) short winters, hot and fairly hot & humid summers.
In the south: hot and humid summers, mild winters. No spring or fall to speak of. Hurricanes create major disasters on average every 30 years (more frequent depending on location) anywhere along the Gulf, Florida, and Carolina coasts.
In Arizona: Long, extremely hot summers. 100+ most of it, 110+ for about 2-3 weeks. Live here if you like to keep a permanent tan or like to live indoors almost all day every day in the summer.
ND/SD/WY/ID/MT/MN: Long, bitter cold winters. Short mild summers. Either there's no mountains (in the eastern areas) or no people (western areas).
WA/OR: Rain. Enough said.
East coast: urbania
everywhere. Horrible traffic situation.
I'm great at pigeonholing the USA.
