WASHINGTON, United States (AFP) — The United States (US) has endured its hottest summer on record, a new peak that scientists said should send alarm bells ringing over the increasingly dire impacts of climate change.

The average temperature for the contiguous US states — excluding Alaska and Hawaii — in the June-to-August period was 74.4F (23.6C), exceeding the previous record, set in 1936 and 2021, by 0.4F, the National Oceanic and Atmospheric Administration said Wednesday.

That means that four of the hottest summers on record occurred within the past five years, with 2022 and 2024 taking fourth and fifth place respectively, with human-caused climate change due mainly to the burning of fossil fuels looming large over the trend.

This year also saw the warmest August since records began in 1895, with average temperatures of 75.6F.

NOAA had previously announced that July 2026 was the hottest of all months ever recorded in the United States.

“This is occurring exactly as forecast by scientists literally decades ago,” Andrew Dessler, a climate scientist at Texas A&M University, told AFP.

“The interesting question is not whether we will keep breaking heat records (we will), but whether we’re going to do anything about it or just stand there while the climate train runs us over.”

The so-called “Dust Bowl summers” of the 1930s — especially that of 1936 — were fueled by drought and extreme heat combining with overplowing across the Great Plains.

“We’ve eclipsed the summer of the Dust Bowl drought of 1936, but just by a hair, it’s like a photo finish,” Karin Gleason, chief of the monitoring section of NOAA’s National Centers for Environmental Information, told AFP.

She explained that while 1936’s record was driven by extreme daytime highs, the 2026 record was driven by unusually warm overnight lows — a result of overall global warming that lets the atmosphere hold more moisture, which keeps nights from cooling off as much.

“The record summer is certainly in line with what we expect from human-caused climate change; as the US and the planet as a whole warms, heat waves become both more frequent and more intense,” climate scientist Zeke Hausfather of Berkeley Earth told AFP.

“It should absolutely send alarm bells ringing, as these hotter summers lead to increased heat stress, higher energy demand for cooling, and strain on infrastructure and public health systems.”

Precipitation was below average, ranking in the driest third on record for both August and for the June-August period, and drought covered nearly 60 per cent of the contiguous US by September 1.

Notable events included Lake Mead, America’s largest reservoir, dropping to its lowest level on record. Elsewhere, severe storms brought heavy rain, including in central Indiana.

Beyond those 48 states, Alaska’s average temperature during August and average summer temperature ranked in the warmest third on record, while Hawaii saw its third warmest August and a summer that fell into the warmest third.

Hawaii was also exceptionally wet: Hurricane Lala brought heavy rainfall, contributing to its second-wettest August on record.

The data comes as a strengthening El Niño pattern, expected to be the most intense in decades, begins to unleash extreme weather across much of the globe.

It is predicted to peak between October and December and fuel record heat in 2027. But because of this El Niño’s extreme strength — with near-record ocean temperatures already seen in the tropical Pacific — it could even push 2026 past 2024 as the hottest year on record.

“The flip side of that is that we can prevent this from getting worse,” University of Pennsylvania climatologist Michael Mann told AFP.

“The consensus among climate scientists is that surface warming of the planet will stop when we reach zero carbon emissions, and we have the clean energy technology to do this. It’s simply a matter of finding the political will.”