Persistent Heat Dome Intensifies Over Southern US

Extreme Heat Conditions in the South-Central United States

A heat dome has reestablished itself across the south-central United States, causing temperatures to climb toward triple digits as the autumn equinox nears. This event prolongs one of the most intense warm spells recorded for states like Texas, Oklahoma, and Arkansas, among others. Millions are exposed to hazardous heat, deteriorating air quality, and possible storms forming at the dome’s edges as it spreads east.

Formation of Heat Dome

The latest heat dome developed over Texas, Oklahoma, Arkansas, Louisiana, and the Southeast, where high pressure has remained since spring. Despite the weaker sun approaching the equinox, temperatures continue to be 5 to 10 degrees above historical averages with highs in the upper 80s to 90s. Dallas, Austin, and Oklahoma City are experiencing temperatures approaching 100 degrees through Saturday.

According to Alan Reppert, Senior Meteorologist at AccuWeather, several factors contribute to the prolonged heat dome across the southern U.S. Beyond the influence of El Niño, sea surface temperatures are favorable for keeping the dome in place. While El Niño’s impact is more pronounced in winter, other ocean-driven signals have continued to dominate late-summer weather patterns.

Record-Breaking Heat Days

The heat dome is intensifying an already harsh season. Dallas has seen 49 days at or above 100 degrees, almost twice its 20-year average, and Oklahoma City has surpassed its typical count threefold. In September, Oklahoma City has experienced 10 triple-digit days, while Dallas has recorded 12 such days.

Towns like Austin have recorded 43 days above 100 degrees, compared to an average of 29 over 20 years. El Paso has had 52 days above 100 degrees, well beyond its usual 34. Cities like Little Rock, Tulsa, and Wichita have doubled or tripled their long-term averages.

The Role of Ocean Temperatures in Sustaining Heat

Warm ocean temperatures continue to reinforce the heat dome. Reppert mentions that while El Niño partly influences this pattern, high sea surface temperatures in the West and Gulf Coast help maintain high-pressure areas.

August 2026 tied July 2023 as the hottest month recorded, with global average surface temperatures at 16.96°C (62.5°F). Additionally, sea-surface temperatures outside polar regions reached record highs with daily peaks at 21.11°C on August 24 and 25.

Vulnerability under the Heat Dome

The dome affects areas already prone to heat conditions. Oklahoma, Texas, and Arkansas have experienced excessive heat. Western Texas and Oklahoma may have slightly cooler temperatures due to their higher elevation, reducing heat effects slightly.

High humidity and stagnant air continue to deteriorate air quality across several states. Vulnerable populations like older adults, outdoor workers, and individuals without consistent cooling face increased risks.

Meanwhile, regions in the Northeast are preparing for their first frost, underscoring the contrasting regional temperatures.

Storms at the Dome’s Boundaries

As witnessed all summer, storms form where the dome’s edges meet cooler air. This week, such storms are expected from the Dakotas and eastern Montana toward the Northeast, involving the Midwest.

A potential storm could form off the Atlantic Coast, potentially drifting across Florida into the Gulf of America. Additionally, an area southeast of Bermuda has a possibility of developing into a tropical or subtropical depression.

These edge-dependent storms have been prevalent where hot, stagnant air meets cooler zones.

Global Heat and Future Outlook

While the southern U.S. heat dome contributed slightly to August’s global record, Europe experienced larger temperature deviations from historical averages according to Reppert. Relief begins to surface as a more active northern Pacific jet stream could disrupt the heat dome, potentially providing relief to the southern U.S.

The extreme summer temperatures have already set records. July saw record-breaking averages of 76.9 degrees across the Lower 48, surpassing historical highs from 1895 and exceeding the extreme heat of July 1936. With heat domes continuously developing since spring, the south-central U.S. endured one of its hottest seasons.

For further information, feel free to contact Newsweek editors, Samantha Beech and Gray R. Thomas.