A summer that started early across the US has no intention of quitting, even as the calendar turns to autumn.

The culprits? El Niño and climate change, which contributed to this summer’s record-breaking warmth and are delaying pumpkin spice season.

Forecasters with the US Climate Prediction Center continue to see increased odds for hotter-than-normal temperatures across much of the country through at least the end of September.

Computer models show a pronounced ridge pattern, an atmospheric arrangement that can lock in sustained spells of warmer-than-normal conditions. This setup will feature widespread unseasonable warmth throughout the country, a pattern consistent with a strong El Niño. The greatest odds of above-normal temperatures exist around the Upper Midwest and the Deep South. Some models suggest temperatures could run 5 to 10 degrees Fahrenheit above normal for the latter half of September.

The blast of unseasonably warm air comes after the hottest summer in US history in a year in which tens of thousands of heat records have fallen across the US. That includes nearly 44,000 record daytime highs and more than 53,000 record-high overnight minimum temperatures recorded at weather stations across the country. Thousands more monthly and all-time heat records have fallen since the start of 2026. Over the same period of time, only about 21,500 low-temperature records fell, or around one cold record for every four heat records.

Many of the busted records date back more than a century. Salt Lake City hit 109 degrees Fahrenheit on July 12, for example, marking its hottest-ever temperature since records began in 1874. Washington, DC, tied its all-time warmest overnight low of 84 degrees Fahrenheit on July 3, where daily observations date back to 1871.

The heat hasn’t relented, despite the calendar turning to September. Even areas that typically escape countrywide heat waves have suffered. Much of Southern California endured excessive heat warnings during the second week of September as hot conditions and soupy air made Rodeo Drive feel more like Bourbon Street.

Why Has Fall Started So Hot?

Climate change is far and away the primary driver of the extreme heat baking the US. Rising average temperatures raise the baseline for extreme heat, making very hot days even steamier now than they would’ve been just a few decades ago.

That trend has been especially notable at night: Many communities across the country have also seen a precipitous increase in overnight temperatures during the warm months as both temperatures and mugginess increase. The lack of relief is what makes heat waves particularly deadly; without beneficial overnight cooling, heat stress becomes too much for many people to withstand.

A warmer climate is also altering upper-level patterns in a way that’s more favorable to extreme heat events. Strong centers of high pressure aloft force air to sink toward the ground. This air heats up as it compresses, combining with intense sunshine and dry soils to ratchet the heat well above normal. These ridges, often called heat domes, are more common in a warming world.

When Will the Heat End?

While overall highs for the remainder of September won’t be as extreme as they are in July, many areas will continue to endure summer-like heat.

El Niño is also lurking in the background. This pattern of warmer-than-normal waters in the Pacific Ocean affects weather patterns around the world.

We typically feel El Niño’s greatest effects during the cold months as these abnormally warm ocean temperatures alter the jet stream, which are responsible for weather patterns during the autumn and winter months.

This year’s El Niño is shaping up to be a record-setting event. Each El Niño is different, but the patterns during previous strong El Niños suggest that a vast swath of the US is in for overall warmer-than-normal temperatures through the fall and winter. In other words, we’re likely not done breaking heat records yet this year.