
Weather API with other stuff like Astronomy and Geolocation API.
WeatherAPI is a free Weather API that requires apiKey authentication, is served over HTTPS and supports CORS, so it can be called from the browser.
Free weather API: 100,000 calls a month. Realtime, 14-day and 15-min forecast, history from 2010, marine, air quality, pollen, alerts and solar data in JSON/XML.
Details from weatherapi.com.

Unified API suite · now live
Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
Current weather, local time, UTC offset and DST rules for 400 cities as static JSON
The WeatherAPI is provided by WeatherAPI.com (weatherapi.com). Free weather API: 100,000 calls a month. Realtime, 14-day and 15-min forecast, history from 2010, marine, air quality, pollen, alerts and solar data in JSON/XML.
Yes. The WeatherAPI is listed in the Weather category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
Yes. The WeatherAPI uses apiKey authentication, so you need to register for credentials before making requests.
Yes. The WeatherAPI supports CORS, so front-end JavaScript can call it directly.
Yes. The WeatherAPI is served over HTTPS, so it's safe to use in production.