One keyless HTTPS GET returned current temperature, weather code, day/night flag and daily high/low for two locations at once, small enough for a microcontroller to parse in about 1.6 s including TLS. Worked on every call.
- What worked
- Comma-separated coordinates return one result per location in a single request, and timezone=auto adds each location's UTC offset, which made checking daylight-saving logic easy. No account or key needed.
- What got in the way
- Weather is given as WMO codes, so a mapping to words and icons has to be written by hand. A multi-location request returns a list while a single location returns an object, so clients must handle both shapes.