Global ocean temperatures have hit the highest level on record, in a worrying sign that this year’s predicted Super El Niño which could bring more extreme weather conditions around the world.

Climatologists confirmed that sea surface temperatures outside of the polar regions reached 21.1C (70F) on August 22.

It broke the previous record set in March 2024, when daily average sea temperatures peaked at 21C (69.9F).

The El Niño system is developing in the tropical Pacific, driving a huge build-up of warm water stretching out towards Oceania.

The weather phenomenon, which was last week described as ‘unprecedented’ in its scale this year, is forecast to bring storms and floods to some parts of the world and drought to others.

El Niño is associated with sea temperatures in the eastern Pacific rising 0.5C above the long-term average. It affects rainfall and average temperatures worldwide.

Experts say the phenomenon is adding further heat to an ocean which has already been warming over many decades due to climate change.

Temperatures are already around 2.6C (4.7F) above the long-term seasonal average, and experts say worse is to come.

Global ocean temperatures have hit their highest daily average ever recorded, reaching 21.1C on August 22

According to the Met Office’s latest predictions, warming in the Pacific could reach 3C (5.4F), while some reports project an increase as high as 4C (7.2F).

The figures from the Copernicus Climate Change Service also mean that August 22 was the hottest August day for the world’s oceans since records began, beating the previous record set in 2023.

Samantha Burgess, strategic lead for climate at the European Centre for Medium-Range Weather Forecasts, said: ‘This record is another clear signal of an ocean under growing stress.

‘El Niño is adding heat to the system, but it is doing so on top of decades of human-driven warming.’

The record-breaking day comes at an especially worrying time for the global weather outlook.

Sea surface temperatures usually peak in March or April, when the ocean has had time to warm after the summer in the Southern Hemisphere.

The fact that we are now seeing a record-breaking day in late August illustrates just how severely El Niño is already affecting global weather.

The El Niño Southern Oscillation is a naturally occurring climate cycle that shifts from hot El Niño years and cool La Niña years once every two to seven years.

As we enter an El Niño phase, the powerful trade winds that normally blow hot water across the Pacific towards Australia weaken, or even reverse.

That prevents cool waters welling up from the deep ocean below and causes hot water to collect near the surface off the west coast of South America.

Scientists say that El Niño has added to ocean heating caused by climate change, pushing temperatures to their highest point on record 

Eventually, that warm water starts to spread out, raising the average global temperature and causing major disruptions to weather patterns around the globe.

Right now, that warming is reaching ‘unprecedented’ levels, with experts warning that an El Niño is building on a scale unlike anything seen since the 19th century.

Last week The Met Office said this year’s El Niño could be ‘the largest since the 19th century’.

‘We should be clear that this is an unprecedented event,’ Professor Adam Scaife, head of long-range forecasting at the Met, added.

Professor Scaife told BBC Radio 4’s Today programme: ‘I have not seen an event like this developing in our forecasts before. And assuming the forecasts are correct – and many other centres are giving the same signals – then we’re expecting the biggest El Niño for over a century, peaking at something over 3C. That is unheard of in modern climate records.

‘We already see signals for increased rainfall and storminess in the autumn here in the UK around November time.’

A Super El Niño could also make next year the hottest on record in the UK.

This comes as experts warn of an ‘unprecedented’ El Niño event developing in the equatorial Pacific, which could send temperatures more than 3C (5.4F) above the long-term seasonal average

Experts warn that the Super El Niño will cause wetter and stormier weather in the UK during autumn and winter 

Most of the heating associated with the El Niño is localised around the Equatorial Pacific Ocean, but the effects are already starting to be felt globally.

Last month was the hottest July on record for the oceans outside the polar regions, with temperatures sitting at 20.9C (69.7F).

Meanwhile, Europe’s coastal regions have been battered by a succession of marine heatwaves that have sent temperatures soaring.

The impacts of El Niño are expected to be particularly impactful because they come on top of decades of ocean warming brought about by human-caused climate change.

While El Niño itself is not caused by climate change, this combination means average temperatures are likely to be much higher than they naturally would be.

Warming oceans threaten coastal communities and low-lying areas because water expands as it gets hotter, leading to sea level rises.

Hotter ocean temperatures also increase the likelihood of extreme weather, such as tropical storms and hurricanes.

Ms Burgess adds: ‘As ocean temperatures continue to rise, the risks to marine ecosystems and coastal communities also increase.

‘The consequences are already visible: the number of marine heatwave days globally has more than tripled since the early 1990s, putting increasing pressure on marine ecosystems and the communities that depend on them.’