the UV index in the Forecast API is based on GFS, while the Air Quality UV index is using "CAMS global atmospheric composition forecasts". CAMS only offers 40 km resolution and 5 days forecast, therefor I am not using it in the regular Forecast API.

CAMS is however more precisely calculating the biologically effective UV radiation dose, while GFS is using a simplified approximation. Because GFS has a higher resolution, accuracy should still be comparable.

In my experiences the GFS based UV index seems to be slightly higher than CAMS. When comparing to other data sources, please make sure the index definition is the same. I noticed some APIs which use 1 as a base value, which could be misleading.

Expand full comment
Mar 27·edited Mar 27

Hi and thanks for your great work. Is ti normal that the precipitation_probability_max returns null in the last 4 days using 14 days forecast? Check this


Expand full comment


I'm checking and comparing UV index from 'Weather Forecast API' and 'Air Quality API' and I get different values for the same location. Comparing with other sources, I'd say that the one from 'Air Quality API' is slightly more accurate.

Can you explain the source of this discrepancy between the two?

Thanks a lot!

Expand full comment

Hey Patrick. Thanks for your hard work on this. All temperature data after day 8 on the 16 day forecast is returning null. Any ideas what is causing this?


Thanks again!

Expand full comment