Since you seem to be informed here, how would one look for places like this that are explicitly not hot & humid, or nearly tropical locations? Effectively a climate and geography filter on this site with "has winters, mountains, summer highs typically < 90 degrees"
Guanajuato city, Mexico. I lived there for a while, <$1k no problem. Not humid, perfect climate. Adorable place. I ended up there because I did some analysis of climate data for all of Mexico and it came out on top.
Edit: I lived there 5 years ago and USD$1k per month would have been plenty, but a nomad website I just looked up lists it at $1250. I'm surprised by that, I think you would be fine. In fact I know people who live there who don't earn anything near $15k USD per year.
Both Korea and Georgia would fit the bill here, except maybe the midsummer months, which are pretty hot & sweaty in Seoul. You may be able to take the edge off by living at higher altitude or by the sea.
Seoul is great but it has huge variatuon in weather. It's like the east coast of the US where you get a nice month and a half of spring and a nice month and a half of fall and everything else is far to one extreme
