US had hottest March on record as nation faced ‘unprecedented’ heat. The continental US registered its most abnormally hot month in 132 years of records, according to Noaa data

 

A person wears a hat while walking along the Strand in Redondo Beach, California, on 20 March 2026, during a heatwave. Photograph: Patrick T Fallon/AFP/Getty Images

 Associated Press

March’s persistent unseasonable heat was so intense that the continental United States registered its most abnormally hot month in 132 years of records, according to federal weather data. And the next year or so looks to turn the dial up on global warmth even more, as some forecasts predict a brewing El Niño will reach super strength.

Not only was it the hottest March on record for the US but the amount it was above normal beat any other month in history for the lower 48 states. March’s average temperature of 50.85F(10.47C) was 9.35F (5.19C) above the 20th-century normal for March.

That easily passed the old record of 8.9F set in March 2012 as the most abnormally hot month on record – regardless of the month of the year – according to records released on Wednesday by the National Oceanic and Atmospheric Administration (Noaa).

 

The average maximum temperature for March was especially high at 11.4F above the 20th-century average and was almost a degree warmer than the average daytime high for April, Noaa said.

Six of the nation’s top 10 most abnormally hot months have been in the last 10 years. This February, which was 6.57F above 20th-century normal, was the 10th highest above normal.

“What we experienced in March across the United States was unprecedented,” said Shel Winkley, a meteorologist with Climate Central, a non-profit science research group.

“One reason that’s so concerning is just the sheer volume of records, all-time records that were set and broken during that time period,” Winkley said. “But also this is coming on the heels of what was the worst snow year. And the hottest winter of record.”

April 2025 to March 2026 was the warmest 12-month period on record in the continental United States, according to Noaa.

On 20 and 21 March, about one-third of the nation felt unseasonable heat that would have been virtually impossible without human-caused climate change, Climate Central calculated.

More than 19,800 daily temperature records were broken for heat across the country, according to meteorologist Guy Walton, who analyzes Noaa data. More than 2,000 places set monthly records for heat – harder to break than daily records – Walton calculated. That’s more March heat records set just last month than in entire decades in the past.

All those broken records “tells us that climate change is kicking our butts”, said Jeff Masters, a Yale Climate Connections meteorologist.

“January through March period was the driest on record for the contiguous US. So not only was it hot, it was record dry as well,” Masters said. “And that’s a bad combination for water availability, for agriculture, for river levels, for navigation.”

The European climate and weather service Copernicus and Noaa are both forecasting a “super” strong El Niño to form in a few months and intensify into the winter.

“A strong El Niño could plausibly push global temperatures to new record levels in late 2026 and into 2027,” Victor Gensini, a Northern Illinois University meteorology professor, said.

Mystery heatwave warms Pacific Ocean to new record

Mark Poynting and Matt McGrathBBC News Climate and Science

 

 

The waters of the north Pacific have had their warmest summer on record, according to BBC analysis of a mysterious marine heatwave that has confounded climate scientists.

Sea surface temperatures between July and September were more than 0.25C above the previous high of 2022 - a big increase across an area roughly ten times the size of the Mediterranean.

While climate change is known to make marine heatwaves more likely, scientists are struggling to explain why the north Pacific has been so hot for so long.

But all this extra heat in the so-called "warm blob" may have the opposite effect in the UK, possibly making a colder start to winter more likely, some researchers believe.

"There's definitely something unusual going on in the north Pacific," said Zeke Hausfather, a climate scientist at Berkeley Earth, a research group in the US.

Such a jump in temperatures across a region so large is "quite remarkable", he added.

The BBC analysed data from the European Copernicus climate service to calculate average temperatures between July and September across a large area of the north Pacific, sometimes known as the "warm blob".

The region extends from the east coast of Asia to the west coast of North America, the same area used in previous scientific studies.

The figures show that not only has the region been warming quickly over the past couple of decades, but 2025 is markedly higher than recent years too.

 

That the seas are getting hotter is no surprise. Global warming, caused by humanity's emissions of carbon dioxide and other gases, has already trebled the number of days of extreme heat in oceans globally, according to research published earlier this year.

But temperatures have been even higher than most climate models - computer simulations taking into account humanity's carbon emissions - had predicted.

Analysis of these models by the Berkeley Earth group suggests that sea temperatures observed across the north Pacific in August had less than a 1% chance of occurring in any single year.

Natural weather variability is thought to be part of the reason. This summer has seen weaker-than-usual winds, for example. That means more heat from the summer sunshine can stay in the sea surface, rather than being mixed with cooler waters below.

But this can only go so far in explaining the exceptional conditions, according to Dr Hausfather.

"It certainly is not just natural variability," he said. "There's something else going on here as well."

 

One intriguing idea is that a recent change to shipping fuels might be contributing to the warming. Prior to 2020, dirty engine oil produced large amounts of sulphur dioxide, a gas harmful to human health.

But that sulphur also formed tiny, Sun-reflecting particles in the atmosphere, known as aerosols, which helped to keep a lid on rising temperatures.

So removing that cooling effect in shipping hotspots like the north Pacific could be revealing the full impact of human-caused warming.

"It does seem like sulphur is the primary candidate for what's driving this warming in the region," said Dr Hausfather.

Other research suggests that efforts to reduce air pollution in Chinese cities has played a role in warming the Pacific too.

That dirty air did a similar job to shipping in reflecting sunlight away, while cleaning it up could have had the unintended consequence of allowing more ocean heating.

Possible impacts for the UK?

The north Pacific's marine heatwave has already had consequences for weather on both sides of the Pacific, likely boosting very high summer temperatures in Japan and South Korea and storms in the US.

"In California, we've seen supercharged thunderstorms because the warm ocean waters in the Pacific provide heat and moisture," said Amanda Maycock, professor in climate dynamics at the University of Leeds.

"In particular, there are things we call atmospheric rivers… bands of air, which contain very high amounts of moisture that fuel themselves from the ocean waters," she added.

"So if we have warm ocean waters… they can then bring a lot of moisture onto the land, which then falls out as rain, or in the wintertime can precipitate out as snow."

 

Long-term weather forecasting is always challenging, but extreme heat in the north Pacific has the potential to affect the UK and Europe in the coming months too.

That's because of relationships between weather in different parts of the world known as teleconnections.

"Although the current warm conditions are located in the north Pacific, these can generate wave motions in the atmosphere that can alter our weather downstream into the north Atlantic and into Europe," said Prof Maycock.

"That can tend to favour high-pressure conditions over the continent, which brings us more of an influence from the Arctic, where we have colder air," she added.

"That can be drawn over Europe and bring us colder weather in early winter."

A colder outcome is by no means certain, as this is a complex area of science. Several other weather patterns also affect UK winters, which are typically getting milder with climate change.

And a warm north Pacific appears to have different effects later in the winter, favouring milder and wetter conditions in some parts of Europe.

Emerging La Niña in the tropical Pacific

Another factor to throw into the mix is what's happening further south in the eastern tropical Pacific.

There, surface waters are unusually cool - a classic sign of the weather phenomenon known as La Niña.

 

La Niña, and its warm sibling El Niño, are natural patterns, although research published this week highlighted that global warming could itself impact the swings between them.

Weak La Niña conditions are expected to persist over the next few months, according to NOAA, the US science agency.

All else being equal, La Niña generally increases the risk of a cold start to winter in the UK, but also brings a higher chance of a mild end, the Met Office says.

"These two drivers in the north and tropical Pacific will be acting together this winter," said Prof Maycock.

"But since the La Niña is quite weak this year, the extreme warmth in the north Pacific could be more important for forecasting the winter ahead."

Additional reporting by Muskeen Liddar and Libby Rogers