Met Office issues new ‘extreme’ heatwave warning as two areas to bake in 39C | Weather | News

The Met Office has issued a new ‘extreme’ heatwave warning as UK waters could reach ‘severe’ levels next week.

The long-term marine heatwave that has hit UK waters for much of 2026 is expected to intensify next week, with temperatures forecast for 39C.

According to the Met Office, surface waters in northwestern European seas are currently experiencing moderate to severe marine heatwave conditions; numerous areas are classified as “strong” and some as “severe”.

This shows waters rising to temperatures generally expected in August, averaging 2C above normal levels.

Temperatures rose above 4-5 degrees in certain parts of the coastline of England and Wales.

Experts warn that these record-breaking temperatures are likely to have far-reaching consequences on weather systems, global climate and ecosystems, causing shifts in fish populations and causing serious damage to many marine species.

This follows last week’s extraordinary heatwave, fueled in part by climate change, and a sharp rise in sea surface temperatures in recent days caused by a “heat dome” that has become stationary over Europe, trapping heat for several days.

The scorching weather caused temperatures to break the record for hottest June day by more than 1°C, set 50 years ago in the famous summer of 1976. Meteorologists suggest that after a brief cooling period, conditions will warm again next week, with temperatures potentially rising to 39°C in parts of South East England.

This means there will be very limited opportunity for the sea surface to cool down following last week’s heatwave; This raises the possibility that the current marine heatwave could reach an “extreme” classification, a category rarely seen in UK waters, according to the Met Office.

The English Channel is experiencing maritime heatwave conditions throughout much of 2026, making this region particularly susceptible to further warming.

According to Net Weather maps, the UK can expect to see the peak of extreme highs on Thursday 9 July, as London is expected to reach 39°C.

According to Net Weather maps, the temperature in the capital and nearby Berkshire is expected to reach 39 degrees, while Hertfordshire is expected to rise to 38 degrees.

Met Office air-sea interaction expert Dr. Segolene Berthou said: “Such conditions would be highly unusual for UK waters.

“Marine heatwaves around the UK have developed rapidly following the last hot air dome and we are now seeing strong and locally severe conditions widespread.

“With more sunny, calmer weather likely next week, there will be little opportunity for the ocean to release this excess heat.”

Earlier this week, the EU’s Copernicus Climate Change Service and the Copernicus Marine Service confirmed that global sea surface temperatures had exceeded previous records set in 2023 and 2024 for this time of year.

These fresh seasonal highs were expected following the emergence of the El Niño weather phenomenon, which causes rising sea surface temperatures in the tropical Pacific Ocean to drive global temperatures upwards.

El Nino conditions were officially declared by the UN’s World Meteorological Organization (WMO) last month; This corresponds to above-average surface sea temperatures recorded in many ocean regions in recent months.

John K Pinnegar, principal scientist and principal advisor on climate change at the government’s Center for Environment, Fisheries and Aquaculture Science, said: “Marine heatwaves can have significant impacts on ecosystems and wildlife.

“Unusually warm sea temperatures over long periods of time can cause shifts in fish populations, damage important habitats such as seagrass and algae, and increase the likelihood of harmful algal blooms.

“These changes could lead to mass mortality events for some marine species and alter the distribution of commercially important fish and shellfish.

“Prolonged periods of high seawater temperatures could encourage new species to visit UK waters, establishing new populations and potentially shaking up UK ecosystems.”

He highlighted a recent increase in the common octopus population, which is causing “serious negative consequences” for crab and lobster fisheries in South West England.

Despite above-average sea temperatures, the public is still being warned about the real dangers of cold water shock. Holly Clements, head of warning and guidance at the Met Office, said: “As warmer weather approaches, and even in marine heatwave conditions, it is important to remember that the water around the UK is still cold. Entering here unexpectedly could lead to cold water shock.”

The Met Office also advised that wherever possible swimmers should choose RNLI lifeguard beaches, stay between red and yellow flags and call the coastguard on 999 if an emergency arises.