G'day,
Without being silly I could recommend taking part in winter sports such as skiing, snowboarding, etc.
I live in upstate NY and am out and about all the time in winter. I like it, actually. When I was young & thin, I skied.
How hot & sticky do you like it? The US SE is one locale, but I couldn't stand their hot & muggy summers.
San Diego has a great climate and is not too far from hills & mountains. Remember earthquakes.
You might want to check out Oregon & Washington state. Wikipedia can give you the climate on some of the major cities there.
Accuweather & The Weather Channel web sites can give you some climate data.
There are climate maps of the US. Then match them up with geography.
Reno/Carson City might appeal to you.
I hope, this helps.