Mandatory Credit: Photo by Krisztian Elek/SOPA Images/Shutterstock (16968018c)People enjoy the sunny day at the water and on the beach in Broadstairs. Botany Bay is a bay in Broadstairs facing the North Sea, Kent, England. It is one of the seven bays in Broadstairs. Botany Bay is famous about its chalk cliffs and being very popular tourist destination.Botany Bay in Broadstairs, UK – 28 Jun 2026 (Image: Krisztian Elek/SOPA Images/Shutterstock)
The Met Office has issued a fresh ‘extreme’ heatwave warning as UK waters could reach ‘severe’ levels next week.
The prolonged marine heatwave that has gripped UK waters for much of 2026 is set to intensify next week, with temperatures of 39C forecast.
According to the Met Office, surface waters in north-west European seas are currently experiencing moderate to severe marine heatwave conditions, with numerous areas classified as “strong” and some as “severe”.
This indicates that waters have risen to temperatures typically expected in August and are on average 2C above normal levels.
Along certain stretches of the English and Welsh coastlines, temperatures have surged by more than 4-5C.
Beachgoers soaking up the sunshine on Brighton beach in East Sussex (Image: Adam Gerrard / Daily Mirror)
Experts warn that these record-breaking temperatures are likely to have wide-ranging consequences for weather systems, the global climate and ecosystems, prompting shifts in fish populations and causing significant harm to numerous marine species.
This follows a sharp rise in sea-surface temperatures in recent days, driven in part by last week’s extraordinary heatwave, which was fuelled by climate change and a “heat dome” that became stationary over Europe, trapping heat for several days.
The scorching spell saw temperatures smash the record for the hottest June day – set 50 years ago during the infamous summer of 1976 – by more than 1C. Following a brief cooler spell, meteorologists suggest conditions are set to heat up again next week, with parts of South East England potentially seeing temperatures climb to 39C.
This means the sea surface will have scant opportunity to cool following last week’s heatwave, increasing the possibility that the current marine heatwave could achieve an “extreme” classification – a category seldom witnessed in UK waters, according to the Met Office.
The English Channel has been undergoing marine heatwave conditions for much of 2026, rendering this region particularly susceptible to further warming.
Weather maps show next Thursday will be 39C (Image: Net Weather)
According to Net Weather maps the UK can expect to see the extreme highs peak on Thursday, July 9 as London is expected to reach a whopping 39C.
According to the Net Weather maps the capital and nearby Berkshire are expected to reach 39C, with Hertfordshire also forecast to climb to 38C.
Dr Segolene Berthou, air-sea interaction specialist at the Met Office, said: “Such conditions would be highly unusual for UK waters.
“Marine heatwaves around the UK have developed rapidly following the recent heat dome, and we are now seeing widespread strong to locally severe conditions.
“With further sunny and calm 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 have surpassed previous records for this time of year, which were established in 2023 and 2024.
These fresh seasonal highs had been anticipated following the arrival of the El Nino weather phenomenon, which sees rising sea surface temperatures in the tropical Pacific Ocean push up global temperatures.
El Nino conditions were officially declared by the UN’s World Meteorological Organisation (WMO) last month, corresponding with above-average surface sea temperatures recorded across multiple ocean regions in recent months.
John K Pinnegar, principal scientist and lead adviser for climate change at the Government’s Centre for Environment, Fisheries and Aquaculture Science, said: “Marine heatwaves can have significant impacts on ecosystems and wildlife.
“Prolonged periods of unusually warm sea temperatures can lead to shifts in fish populations, damage important habitats such as seagrass and kelp, and increase the likelihood of harmful algal blooms.
Britain could be baking once again soon (file) (Image: Adam Gerrard / Daily Mirror)
“These changes can result in mass-mortality events for some marine species and alter the distribution of commercially-important fish and shellfish.
“Prolonged periods of elevated seawater temperatures can also encourage new species to visit UK waters, establish new populations, potentially shaking up UK ecosystems.”
He highlighted the recent instance of a population surge of common octopus, which has been causing “serious negative consequences” for crab and lobster fisheries in South West England.
Despite above-average sea temperatures, members of the public are still being warned about the very real dangers of cold water shock. Holly Clements, Met Office head of warnings and guidance, said: “With warmer weather approaching, and even with marine heatwave conditions, it’s important to remember that the water around the UK is still cold. Entering it unexpectedly can lead to cold-water shock.”
The Met Office further advised that wherever possible, swimmers should choose RNLI lifeguarded beaches, remain between the red and yellow flags, and call 999 for the coastguard should an emergency arise.