BBC Weather has given its verdict on how long the latest London summer heatwave will last. Yesterday (Tuesday, August 12) temperatures hit 33.4C in parts of London amid the fourth heatwave of the summer.
An amber heat-health alert remains in place until 6pm today (Wednesday, August 13), although slightly lower highs of 29C are expected this afternoon. Forecasters then expect the weather to briefly rise again to 31C on Friday, before settling at 26C for the weekend and early next week.
Marco Petagna, meteorologist at the Met Office, told the PA news agency: “Wednesday will be mostly dry with further very warm or hot sunshine, but we will see some showers, particularly in the South East during the afternoon and also a few affecting Scotland during the day, which could turn heavy and thundery.
“It will be another warm and hot day with maximum temperatures of 33C to 34C, highest in Lincolnshire and Yorkshire. On Thursday there will still be a few showers, particularly in the north, and it will not be quite as hot, but temperatures will still peak around 29C to 30C in East and south-east England.
“Friday looks mostly fine, with very hot sunshine in the south and South East, where temperatures could reach 31C, while Scotland will see highs in the low 20s.”
When will the heatwave end?
To meet the threshold for a heatwave, temperatures must be 3C higher than average for three consecutive days. For London, this means the mercury must rise to 28C to meet the threshold.
Technically, the heatwave comes to an end on Saturday (August 16) when the mercury drops to 26C. But this won’t be the end of the sunny and dry spell with peak temperatures of at least 24C forecast until August 20.
After this, slightly lower peaks of 23C are expected for practically the rest of the month. The Met Office’s long range forecast for early September predicts unsettled conditions will bring an end to this constant sunshine with the potential for strong winds and thunderstorms.
This being said, temperatures in southern England should still be above normal with the chance of some hot spells.
What’s causing this heatwave?
Weather maps show the jet stream weather system is being pushed high above the UK. This, coupled with high pressure, means hot and humid air is able to drift into the country from continental Europe.
Spain, Portugal and France are experiencing extreme heat due to this phenomenon. The French city of Nimes recorded its highest ever August temperature on Sunday as the mercury rose to 41.8C.
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