Heatwave. Quite an exceptional spell of weather for September.
Thanks to Cathy for the photograph.
So the general set-up sees high pressure over the UK, low pressure to the west of Spain/Portugal – and this allows a continental flow, with air originally sourced from Africa. Hence…heatwave.

Today will be hot and sunny – no cloud after any early mist/fog/low cloud patches clear. 29’C, maybe 30’C, though a little bit of a breeze developing. Mostly clear skies overnight though a little high cloud for a time, and one or to patches of mist/fog/low cloud by dawn. A fairly warm night, no lower than 16’C.
Wednesday will be hot and sunny – any early mist/fog/low cloud patches clear. A bit more high cloud around than on Tuesday, but hotter, 31’C, maybe 32’C. Generally more high cloud overnight and temperatures therefore higher, so a warm night at no lower than 18’C – perhaps no lower than 20’C in some spots. Again a chance of some mist/low cloud patches by dawn.
Thursday starts with mist/fog/low cloud in places, but this will clear fairly quickly, and otherwise it will therefore be another day of glorious sunshine – perhaps some high cloud. Again 31’C, maybe 32’C should be achieved. Some high cloud overnight and again some patches of mist/fog/low cloud by dawn, probably more extensive than previous dawns. Some uncertainty over temperatures but broadly another warm night, down to somewhere between 15’C and 19’C.
Friday sees any early mist/fog/low cloud clear fairly quickly, then long spells of sunshine, albeit some high cloud making it hazy at times. Hot, reaching 30’C, maybe 31’C. Clear skies for much of the night, though mist/fog/low cloud developing towards dawn for many places. A warm night, minimums between 18’C and 20’C.
It remains hot into the weekend, with high pressure still in place.

Saturday sees early mist/fog/low cloud patches clear to leave long spells of sunshine. A little bit of cloud bubbling up and an exceptionally small chance of a shower. Likely a shade hotter again, around 32’C. A small chance of a thundery shower overnight, otherwise clear skies and warm, minimum temperatures somewhere between 18’C and 20’C.
Sunday will be another day of long, hot sunshine. A bit of cloud bubbling up and a very small chance of a thundery shower. Around 32’C, maybe a shade more. Another warm night, minimum temperatures somewhere between 17’C and 19’C.
Monday likely remains on the hot and sunny side, though an increasing chance of some showers, perhaps thundery and we should start to ease on the temperatures – somewhere between 25’C and 28’C, depending on sunshine amounts.
Then for the rest of next week we are looking at a gradual normalisation. Not impossible that the hot spell continues a bit longer, but most likely by Tuesday we are down to it being very warm, with more comfortable nights too. And the weather should be more changeable – some sunshine, some cloud, some showers.
Enjoy the hot sunshine, if you can! I fully intend to, after our grumpy July/August.