Will the UK see a 40C heatwave again this summer?

Met Office says no immediate indication of exceptional heat even though there has been ‘persistent warmth for much of the month’

Stuti Mishra
Wednesday 12 July 2023 11:10 BST
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UK weather: The latest Met Office forecast

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Louise Thomas

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As temperatures continue to soar globally, many are left wondering if the UK will experience another scorching 40C heatwave this summer, similar to the year before.

Speculation is rife that the country will get a blistering heatwave this month as weather maps have shown conditions could become hotter in the coming days.

The summer in the UK has already begun on a hotter note, with June temperatures smashing all-time records.

According to the Met Office, last month had the hottest June temperatures since records began.

The early few weeks of the official summer season saw temperatures climbing over 30C, leading to heat-health alerts, water shortages and even unprecedented fish deaths in rivers.

The Met Office said the unusually high heat was caused by “the background warming of the Earth’s atmosphere due to the human-induced climate crisis”.

“What’s striking is the persistent warmth for much of the month, with temperatures widely into the mid 20s Celsius for many and even into the low 30s at times,” said Dr Mark McCarthy, science manager of the National Climate Information Centre.

He explained how last month “started with a good deal of high pressure and temperatures initially around average for many, but once that subsided, warm, humid air began to influence temperatures, with 32.2C the highest temperatures reached”.

June saw an average mean temperature of 15.8C – eclipsing the previous record by 0.9C, while the previous top three Junes were separated by just 0.1C.

The forecaster carried out a rapid study that found that the chances of a June beating the previous record of 14.9C had at least doubled since the period around 1940.

The Met Office’s climate extremes principal fellow and chief meteorologist Paul Davies explained that rising average global temperatures, which stand at 1.2C now, have “driven up the possibility of reaching record high temperatures” in the UK.

The institution defines a heatwave as three consecutive days with daily maximum temperatures meeting or exceeding a heatwave temperature threshold.

That threshold, however, varies across the country, from 25C in Northern Ireland, Scotland, Wales and the north and south west of England, to 28C in parts of south east England.

The UK has so far not experienced the same scorching temperatures in 2023 as last year, when large parts of the country baked in extremely high temperatures that breached the 40C mark for the first time, triggering wildfires, disrupting transport and leading to thousands of premature deaths.

Last year’s extreme heat arrived on the heels of high global temperatures, with several countries in Asia, Africa and Europe shattering records. The World Weather Attribution (WWA) said the heatwave would have been “extremely unlikely” in the absence of the climate crisis.

This year, the signs seem to be aligning once again for a hotter summer. The onset of the El Nino weather phenomenon in the Pacific is expected to drive temperatures higher, with dozens of countries in Asia and Europe already reeling under earlier than usual heat.

Searing heat has continued to blanket much of the US Deep South and parts of Mexico for a third week. The relentless, triple-digit heatwave – exacerbated by climate change – has been blamed for more than a dozen deaths in Texas and Louisiana and a spike in emergency room visits.

Met Office figures show June on track to be the hottest on record
Met Office figures show June on track to be the hottest on record (Met Office)

Looking at these signs, many meteorologists have predicted worsened heat in the coming days arriving in the UK.

The Met Office forecast so far states that the possibility of “above-average temperatures” is higher in the latter half of this week, increasing the likelihood of heatwaves.

The forecaster also clarified last week that there is currently no indication of exceptional heat in the next few days, contrary to media reports of multiple heatwaves hitting the UK.

With changing weather patterns, long-range forecasts are often not entirely reliable, but experts said a return of extreme 40C temperatures cannot be ruled out entirely.

In 2022, the UK experienced three heatwaves
In 2022, the UK experienced three heatwaves (Getty)

Even if temperatures don’t breach the 40C mark, above average heat during the summer can also pose health-related risks to vulnerable populations. According to the UK Health Security Agency, last year’s heatwave played a part in 3,000 deaths in England and Wales.

Various scientific assessments said the frequency and intensity of heatwaves are increasing because of the climate crisis.

“While the UK has always had periods of warm weather, what climate change does is increase the frequency and intensity of these warm weather events, increasing the likelihood of high temperature records being broken, like we saw for 2022’s annual temperature for the UK,” Mr Kendon said.

The world has already warmed by about 1.2C since the industrial era began and the next few years are expected to be the warmest on record, with climate conditions being impacted by El Nino, according to the World Meteorological Organisation (WMO).

Map of global ocean temperatures by NOAA shows water around the UK hitting category 5 marine heatwave
Map of global ocean temperatures by NOAA shows water around the UK hitting category 5 marine heatwave (NOAA)

With continued warming, the world is set to soon breach the crucial 1.5C mark of average global heating. This year, the world has already temporarily breached this mark, set by the landmark Paris Agreement as a target.

The heatwaves have not just wreaked havoc on the land, but global sea-surface temperatures also smashed records in June, with coastal waters along the UK experiencing an “unheard of” marine heatwave.

Meanwhile, the UK government was slammed by its own climate advisers for their slow pace in meeting its “net zero” greenhouse gas emissions target and backtracking on fossil fuel commitments.

The Climate Change Committee (CCC) said Britain has “lost its clear global leadership position on climate action”.

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