Check here i have described the solution https://forums.garmin.com/sports-fitness/cycling/f/edge-explore/154798/weather-widget/1168378?focus=true
This procedure looks rather like a complex unofficial workaround rather than simple solution for end user. Garmin didn't provide official downgrade option or event official old firfmwares. As built-in widget uses temperatore unit, I would expect Garmin adds possibility to set in either in device or in Garmin Connect Mobil App (and sync to device). Garmin is not a small no-name comapny but big brand so should take care of ergonomy and functionality of their devices so finally for his reputation.