September heatwave: Why is it so hot in the UK & when will it end as mercury pushes sweltering 32°C

September usually marks the end of summer in the UK - a time to dust off winter coats and the trusty hot chocolate stash. Well, not in 2023, it seems.

After a wash-out June and July, the UK is now in the grip of an unexpected heatwave, with temperatures pushing 32°C in some areas today (Monday, September 4) as kids return to school. It’s set to remain hot for the rest of the week, especially in the south - although northern areas will still see temperatures widely in the “mid to high twenties”.

Met Office meteorologist Jonathan Vautrey said: “It’s getting hot in here. And temperatures are set to climb over the coming week.

“Many of us will see temperatures widely above average for the time of year and that continues across the southern half of the UK as well – climbing towards 30C, if not 32C, in a few spots as well. We might be into meteorological autumn, but it is giving us something a bit more summery that many of us have been missing.”

But why is it so hot at this time of the year and when will temperatures return to normal? Here’s everything you need to know about the September heatwave.

Why is it so hot?

There are number of factors behind this most recent shift in weather conditions. Firstly, the warmer weather is being linked to a jet stream which has brought largely unsettled weather conditions to the UK in recent weeks.

The Met Office said in its weather report that the jet stream was continuing to shift north from Spain, allowing high pressure to build across the UK. Secondly, the influence of former tropical cyclone Franklin is continuing to move into the north of the Atlantic, amplifying this build-up of high pressure.

Despite an unsettled July and August, this season was still one of the UK’s ten warmest summers on record, according to provisional Met Office figures. But this week could potentially see the highest temperatures of summer 2023, beating the 32.2C record that was recorded on June 10 and 25.

When will the high temperatures end?

Tihis weekend there is a chance of a “breakdown” in the settled conditions although the exact timing of this is uncertain, the Met Office said. Temperatures are likely to return closer to normal during mid September, although they will probably still be above average.

From September 8 onwards, conditions are likely to become more changeable, with an increased chance of rain or showers for all areas, some heavy or thundery. In the second half of September, conditions are likely to vary across the country, with showery rain being most frequent in northwestern areas of the UK.

The southeastern part of the country is expected to be more settled, with a chance of showers at times. The Met Office long range forecast reads: “Confidence in the forecast decreases later in this period; however, a mix of mostly dry weather with occasional wet spells is possible, with a higher incidence of high pressure forecast.

“There is a greater chance than normal of temperatures being above average.”