Hi, creator of Open-Meteo here. The limits are 600 calls / min, 5.000 calls / hour and 10.000 calls / day. Limits are applied on an IP basis.

This is not ideal for shared hosting services like cloudflare workers, but is the easiest and privacy-friendly way to limit access to fair-use.

Additionally, weather data is uploaded to a AWS S3 open-data sponsorship and you can run your own API instances (even commercially). The only draw back is, that a lot of data needs to transferred. I am working on a S3 cloud-native approach, but it is still in testing.

The free tier is cross-financed by commercial customers that use the service for energy forecasting, agriculture planing or wild fire prevention. There is no external funding, VCs, or whatsoever, the code is build in public on GitHub and I intent to continue running the free API service as is.