• https://www.weather.gov/documentation/services-web-api

All of the information presented via the API is intended to be open data, free to use for any purpose. As a public service of the United States Government, we do not charge any fees for the usage of this service

• https://brightsky.dev/

Bright Sky is free-to-use for all purposes

• https://www.dwd.de/EN/service/copyright/copyright_artikel.html

all spatial data and spatial data services available for free access may be used without any restrictions provided that the source is acknowledged

• https://open-meteo.com/en/pricing

Open-Meteo APIs are free for non-commercial use

…

Dunno about “usually”. There’s providers that cost and there’s providers that don’t. There’s certainly multiple free providers available.