It's clearly right on the borderline between 8 and 9 today, as the 7 AM update only has 4 "9s" in the same area as that map I posted.

And yes, it looks like it low ozone levels aloft are partly the cause:

http://www.temis.nl/uvradiation/nrt/uvindex.php?lon=-0.07&lat=51.30

You can enter your own lattitude / longitude figures to get the ozone levels for any area, btw. So for Falmouth, you get:

http://www.temis.nl/uvradiation/nrt/uvindex.php?lon=-5.07&lat=50.15

The 21st (Wednesday) is forecast to have low ozone over the south of the UK. I wouldn't be surprised to see the odd 9 pop up on the forecast nearer the time!

7.8 today

7.1 today in Reading but 8.5 in Camborne. The air's more humid now.

7.3 today.

6.8; hazier, more humid.

Yes, and a 7.6 in Reading so possibly an 8 here at a push. That's getting rid of all that humidity. The Reading graph is spiky, with the sun in-and-out. How was the coastal graph Pictures? I haven't looked at the satellites yet so not sure if you had a sunny day.

Impressive amounts of ozone are in the forecast - and the UV index plummets as a result. A peak of 6.1 under clear skies in late June would be quite remarkable.

http://www.temis.nl/uvradiation/nrt/uvindex.php?lon=-0.07&lat=51.30

London

Date UV
index ozone
column
23 Jun 2017 7.6 310.9 DU
24 Jun 2017 7.7 308.1 DU
25 Jun 2017 7.4 317.9 DU
26 Jun 2017 7.0 328.4 DU
27 Jun 2017 6.3 358.4 DU
28 Jun 2017 6.1 365.2 DU

24 June: only 4.9

25 June: 5.0

26 June: back up to 7.8.

3.7 yesterday and 3.2 today. Not far off the seasonal zenith, these are the lowest readings at Reading for a while. This reflects the high UV and great sunshine we've had- not just quantifiable by hours of sunshine.

3.5 yesterday, 5.0 today (Reading). Still time for some 8s in the south in the next fortnight. Then we can watch the numbers slip down, although expect 6s potentially through most of August.

5.1 yesterday; 7.2 today.

5.7 there. Higher here this afternoon.

6.3, 6.7, 6.2 over the last three days. Good run of sixes but I feel the top numbers are slipping away again.

7.5 yesterday. Slow to get going today in Reading, but strong sunshine here.

7.3 finish for Reading

6.7, 6.3, 3.1 for the last 3 days. Impressive that Reading managed a 3.1 under this!

Several dull days but 6.8 today- I noticed the RH was down this afternoon.

6.6 today .....earlier than now, obviously!

Maxed at 6.8 here today at 1400.

That seems right Roger- 6.7 in Reading.

4.0 today.

Reading reached 6.3 yesterday but an amazing (for August) 7.6 on Saturday!

Edit: looking back that's the highest since 26th June.

Tell me about it - I was out in the fields with the wolves and (between thunderstorms) the sun was searing... the day itself wasn't hot, but boy that sun was strong. The wolves were panting and we handlers were sweating our unmentionables off, as we we were all wearing coats. (And there was a corker of a storm towards the end of the walk as well, booming thunder all around. The wolves, incidentally, weren't at all bothered!)

Still, with the sun losing 0.3° in altitude a day the UV index should decline quite quickly now.

Worth noting that locally factor 6 is forecast from today until Monday. So late in the summer for a 4 day run like this- remember, the sun is only as high as in mid April over the next few days, and 6 is a rare call then. In fact 6 wasn't breached at Reading this year until 11th May.

So make the most of a good tanning/ vit D spell.

Last 3 days (including today) 5.4, 5.4, 5.0 at Reading. So close to 6 each day on the sunny south coast.