Pat - I'm seeing unexpected units (?) in my forecasts on my 32 bit Seagate Dockstar running your latest beta, python 3.8.1, latest v4 weewx beta.
Uncertain what exactly's going on, but it's entirely possible this ancient system has a whacked set of locale(s) installed given it's history.
Other note - I had to hand-compile a 'lot' to get everything working, including python, openssl, a bunch of pip3 modules, etc. That said, other than this one nit it looks like everything is working as expected in the os, weewx, and all the extensions+skins including Belchertown.
Not a big priority - I can just disable forecasts on this system if needed, but I thought I'd mention it.