Summer Heat Isn’t Over: El Niño and Climate Change Could Keep the U.S. Warm Through Fall

Such a summer Record-breaking heat started early across the country—and forecasters say it may continue well into September, delaying the arrival of pumpkin spice season.

Who is to blame? El Niño and climate change have combined to produce record warmth across the United States this summer, with little relief expected as fall begins.

Forecasters at the U.S. Climate Prediction Center say the odds of warmer-than-normal temperatures across much of the country remain high through at least the end of September.

Computer models show a pronounced ridge pattern—an atmospheric setup that can create sustained periods of above-normal temperatures. This widespread, unseasonable warmth is consistent with a strong El Niño. The upper Midwest and Deep South are among the areas most likely to experience hotter-than-normal conditions, while some models suggest late-September temperatures could reach 5 to 10 degrees Fahrenheit above average.

The unseasonable warmth follows the hottest summer in U.S. history, when tens of thousands of heat records were set nationwide. Weather stations recorded nearly 44,000 daytime maximum temperature records and more than 53,000 nighttime minimum temperature records. Since the beginning of 2026, monthly and all-time heat records have fallen by thousands more.

By comparison, there were only about 21,500 cold records during the same period—roughly one cold record for every four heat records.

Many of the broken records dated back more than a century. Salt Lake City, for example, reached 109 degrees Fahrenheit on July 12, its highest temperature since records began in 1874. Washington, D.C., tied its lowest overnight temperature of 84 degrees Fahrenheit on July 3, a daily record dating to 1871.

Even with September underway, the heat has not eased. Regions that typically avoid widespread U.S. heat waves are feeling the effects as well. During the second week of September, much of Southern California faced extreme heat warnings. The combination of heat and humidity made Rodeo Drive feel more like Bourbon Street.

Why Is It Still So Hot in Autumn?

Climate change is the main reason heat waves are becoming more intense across the United States. Rising average temperatures have raised the baseline for extreme heat, making very hot days more humid than they were decades ago.

The trend is especially noticeable overnight. Communities across the country are experiencing rising nighttime temperatures, along with increasing humidity during the warmer months. Without cooler nights, the body has less opportunity to recover from daytime heat, making heat stress more dangerous and difficult to tolerate.

A warming climate is also making upper-level weather patterns more favorable for extreme heat. A strong area of high pressure causes air to sink toward the ground. As the air compresses, it heats up. Combined with strong sunlight and dry soil, this process can drive temperatures far above normal.

These persistent areas of high pressure are sometimes called heat domes, and they are becoming more common in a warming world.

When Will the Heat Finally End?

Temperatures during the rest of September are not expected to be as extreme as they were in July, but many parts of the country will continue to experience summer-like heat.

El Niño is also influencing the outlook. This climate pattern, marked by warmer-than-normal Pacific Ocean waters, can alter weather patterns around the world.

El Niño’s effects are usually strongest during the colder months, when unusually warm ocean temperatures influence the jet stream and shape autumn and winter weather patterns.

This year’s El Niño is developing into a record-setting event. Although every El Niño is different, past strong El Niño events suggest that large parts of the United States could experience warmer-than-normal conditions throughout fall and winter.

In other words, the United States may not be finished breaking heat records this year.