The current “UV average” seems to be over the 24 hour period of the day. Given half of a day has no sunshine, it’s a little pointless.
My thought would be to calculate a 6 hour average, +/- 3 hours from solar noon? That can be calculated as the average of sunrise and sunset of the GPS location (seems sunrise/sunset is already known when I look at my weather report).
Would be way more meaningful to know what the average UV was from say 10am to 4pm?