Mercury set to plunge across UK as short-lived 20C warm blast swapped for bitter eastern chill

Nathan Rao
Wed, 18 Mar 2026 09:14:38 +0000

Britons should make the most of a near-70F heat blast before temperatures dip at the weekend.

A surge from the tropics will rocket the mercury today, which could be the warmest day of the year so far.

Southern and western regions will nudge 20C in the sunshine today and tomorrow with highs widely in the high teens.

But the warm blast will be short-lived, with another U-turn at the weekend sweeping in chilly easterly winds.

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Met Office meteorologist Alex Deakin said: “On Wednesday, to the south there is plenty of sunshine, and we could reach 20C on the west coast of Wales, and these temperatures are significantly above average.

“It is not quite as warm on Thursday, but with light winds, it is going to feel pretty mild for the middle-latter part of March.

“Through Thursday, high pressure sets in and introduces a bit of an easterly flow, and that is going to introduce some cooler conditions.”

The balmy blast will in part be driven by a wildly snaking jet stream, allowing high pressure to build close to Britain.

However, shifting pressure patterns after mid-week will switch mild southerly winds for chilly easterlies.

Deakin said: “As the jet stream drives southwards, it will spin up an area of low pressure, but as the jet stream pushes to the north of the UK, it allows high pressure to build in, and that will bring largely clear skies.

“Some of us will have some warm sunshine through this week, and temperatures dip away again towards the end of the week.

“A weather front is still around on Wednesday night and into Thursday, and it may provide some rain and drizzle.”

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Rocketing temperatures have prompted bookies to take the axe to the odds on this spring smashing the record books.

As temperatures hit a sweltering 20C today, Coral is offering 2-1 from 4-5 on the hottest spring on record.

Spokesman Joh Hill said: “With temperatures reaching close to 20C on Wednesday, we have slashed the odds on this spring being the hottest on record in the UK.

“Hopefully, we can leave the wintry conditions behind us soon and look forward to some glorious sunshine.”

Wednesday is likely to bring the peak of the warm weather with the mercury set to plunge ahead of the weekend.

As high pressure moves northwards, spiralling winds will pick up from an easterly direction, ramping down the thermostat.

Highs at the weekend will hover in high single figures with lows overnight sinking below freezing.

Jim Dale, meteorologist for British Weather Services and co-author of ‘Surviving Extreme Weather’, said: “Wednesday is likely to bring the peak of the warm weather, but it is not going to be long-lived.

“High pressure is going to move northwards by the weekend, and that is going to bring in an easterly.

“So, it is going to feel cooler again as we go into the second half of the month.”