You're used to the climate you grew up in and changing from that can be a waste of time. There's plenty of interesting places all over the world north of any line you choose, say 48 degrees north (adjusting for Gulf Stream, etc).
I moved from coldish (20 deg summers, -10 winters) where I was born and lived 30 years to hot (40+ deg, 15 deg); I work best in well over 40. For me when it drops below 10 it gets annoying but then again people have trouble getting me out of workmode in any circumstance.