Are there any places in the world that maintain like 15-20°C year round?

Say around Oakland California really. It's about 500 miles north of San Diego.

San Diego is far warmer. I went to school in San Diego county. Heck even LA is far warmer further north.

Seen it as high as 35° c. (95°f) In San Diego. Far higher inland.

San Diego California is close to that on the coast. If gets a little warmer in the summer, but not much.

Essaouira in Morocco has that kinda weather pretty much. It is often cool & breezy but can get quite windy at times

The pacific northwest is close to that on the west side of the Cascades. . In Tacoma the Average is about 12°. About the same in Seattle and Olympia.

Tbh thats an ideal temp for me. Not too hot. And hopefully nice and cool in shady areas etc. Anyway im here to see where those places are lol

Mid-latitudes in the northern and southern hemisphere would fit in that rough category.