I also have this some times i get full sun icon when <5% but always full cloud when >5% and in my case <35%
I did post a thread called solar icon, about this on 17/05/2004 but had no reponses but at least i know im not the only one now.
Have uploaded these to show
this one the solar is 15.6% (not easy to read)
what might be happening is that half an hour after sun rise and or half an hour before sun set, wd boosts the solar value to use for sun shine hours…and that might be what is happening…even though the raw value is still low
i.e does it happen just aropund sunrise/set?
i have seen this myself on my station at the farm
Sunset with me tonight was 21:49 BST and the reason the screen shots show the icons they do at those times was because it clouded over, and this happens during day when it clouds over as well