Normally, by now, there would have been a couple of '9's at Camborne, virtually always associated with some sea mist conditions, but there's been a lack of the warm sector humid ridges required. Very low UV year so far.
The only real '8' was on Monday, Tuesday saw a spike well into 8, & may have been higher if there not been a fairly persistent cloud cover.
Yesterday's dry air behind the front saw a fall in the UV at Camborne compared with recent days, the lowest since 30th May, which I would have expected. (Deep blue skies so the forecast went up from 7 to 8).
I think, from my non technical viewpoint, the air's still too much of a returning polar maritime for it to go up much. As Freddie says, certain aspects are favourable, but low level moisture is far too low, the aspect that the forecasts seem to ignore.. May creep towards 8 but that's just normal. Under ideal conditions Camborne & Scilly have recorded 10 during June.
If Nick G's reading this, it would be interested to get some UV reports.
If I'm wrong & it hits a 9, I'll take it all back! It will also cause me a bit of confusion.