alt Hacker NewsDoes anyone know how UV indexes reported by weather apps (including forecasts) work?
I've found that some sources report lower UV index on cloudy days, whereas some seem to indicate the same index as a sunny day.
It's not clear if these sources all have a different model for UV, some being more sophisticated or conservative, and whether any of them are backed up by a UV meter.
It is a prediction of UV intensity based on specific forecast location, time of day, day of year, prevailing weather, and any anomalies affecting the ozone layer. It is calculated by NOAA.
https://www.cpc.ncep.noaa.gov/products/stratosphere/uv_index...