El Niño and Climate Change Prolong Summer Heat Across US
Record-breaking temperatures persist into autumn due to atmospheric patterns.
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1Prolonged summer heat
Unseasonably warm temperatures continue across much of the US through September, defying typical autumn patterns. The US Climate Prediction Center forecasts increased odds for above-normal temperatures nationwide. Computer models show a pronounced ridge pattern locking in sustained warmth, particularly affecting the Upper Midwest and Deep South. Some regions may experience temperatures 5-10°F above normal for late September.
2Record-shattering summer
2026 brought the hottest US summer on record, with tens of thousands of heat records broken nationwide. Weather stations recorded nearly 44,000 daytime highs and over 53,000 record-high overnight minimums. The ratio of heat records to cold records stands at approximately 4:1 since January 2026. Many surpassed records dated back over a century, including Salt Lake City's 109°F on July 12 (since 1874) and DC's 84°F overnight low on July 3 (since 1871).
3September heat anomalies
Even typically cooler regions experienced extreme heat in early September. Southern California faced excessive heat warnings, with conditions making Rodeo Drive feel like New Orleans' Bourbon Street. The persistence of heat into autumn months demonstrates climate change's impact on seasonal patterns. Unlike typical summer heat waves, this event shows broader geographical coverage and longer duration.
4Climate change mechanisms
Rising average temperatures elevate the baseline for extreme heat events. The warming climate particularly affects nighttime temperatures, reducing crucial cooling periods. This creates dangerous conditions as heat stress accumulates without overnight relief. Upper-level atmospheric patterns now more frequently produce heat domes - high-pressure systems that trap and intensify warm air at ground level.
5Heat dome dynamics
Heat domes form when strong high-pressure systems aloft force air downward, compressing and heating it. Combined with intense sunshine and dry soils, these systems can elevate temperatures well above seasonal norms. In a warming climate, such atmospheric configurations become more common and persistent. The current pattern shows characteristics typical of climate change-influenced weather systems.
6El Niño's growing influence
The developing El Niño event, characterized by warmer Pacific Ocean waters, is expected to strengthen through fall and winter. Historical patterns during strong El Niño years suggest widespread above-normal temperatures across the US. While El Niño's peak effects typically occur in colder months, its early influence may contribute to prolonged warm spells. This year's event could become record-setting.
7Public health impacts
The lack of nighttime cooling creates particularly dangerous conditions for vulnerable populations. Sustained heat stress without relief leads to increased heat-related illnesses and mortality. Urban areas face compounded effects due to the urban heat island phenomenon. Public health systems must prepare for extended heat seasons as these patterns become more frequent.
8Long-term climate trends
The current heat patterns align with projections of climate change impacts on weather systems. The increasing frequency and intensity of heat waves, along with shifting seasonal boundaries, demonstrate measurable climate shifts. These changes affect energy demand, agriculture, and ecosystem balances. The 2026 heat records may represent a new normal rather than anomalies as global temperatures continue rising.
Original article: Science Latest — El Niño and Climate Change Prolong Summer Heat Across US