A new heat dome has settled over the south-central United States, driving temperatures close to triple digits as the region nears the autumn equinox. This heatwave prolongs one of the most extreme warm spells recorded in Texas, Oklahoma, Arkansas, and neighboring areas. Millions are facing another week of severe heat, deteriorating air quality, and the potential for storms along the dome’s periphery as it spreads eastward.

Persistent Heat in Texas and Oklahoma

The latest heat dome has formed over Texas, Oklahoma, Arkansas, Louisiana, and parts of the Southeast. These areas have experienced prolonged high pressure since spring. Despite the sun weakening with the approaching equinox, temperatures are 5 to 10 degrees above normal. Highs in the upper 80s and 90s are common, with Dallas, Austin, and Oklahoma City pushing towards 100 degrees.

“There are multiple reasons for this heat dome to be so persistent across the southern US,” said Senior Meteorologist Alan Reppert from AccuWeather, citing oceanic influences beyond El Niño.

According to Reppert, El Niño’s impact typically becomes stronger in winter. This delay allows other sea temperature patterns to dominate late summer weather.

Record-Setting Heat Streaks

The heat dome compounds an already harsh season. Dallas has experienced 49 days at or above 100 degrees, nearly double its 20-year average. Oklahoma City has exceeded its usual count by more than three times. September has brought 10 days of triple-digit temperatures to Oklahoma City and 12 to Dallas, an unusual but not unknown occurrence.

“While 100-degree days in September are impressive, they have been recorded before,” added Reppert.

Other cities are also nearing historic numbers. Austin has seen 43 days above 100 degrees, compared to an average of 29. El Paso recorded 52 such days, far exceeding its typical 34. Little Rock, Tulsa, and Wichita have doubled or tripled their long-term norms.

Ocean Temperatures and the Heat Dome

Warm ocean waters are strengthening the heat dome. “El Niño and sea temperatures contribute to this heat dome,” Reppert explained. Warm waters off the West Coast and the Gulf of Mexico bolster the ridge.

August 2026 matched July 2023 as the hottest month globally, with average temperatures reaching 16.96°C (62.5°F). Sea-surface temperatures outside polar regions hit record highs, averaging 21.07°C.

Who Is Most at Risk

The dome covers some of the country’s most heat-prone areas. “Most of Oklahoma, Texas, and Arkansas are vulnerable, with western regions slightly cooler due to higher elevation,” Reppert noted.

High humidity and stagnant air lead to poor air quality. Vulnerable populations, such as older adults, outdoor workers, and those without cooling, face increased risks as the pattern persists. Meanwhile, parts of the Northeast prepare for their first frost, highlighting regional temperature differences.

Storms at the Dome’s Edge

The dome’s boundaries fuel thunderstorms. This week, storms are predicted from the Dakotas and eastern Montana to western Minnesota, the Midwest, and the Northeast.

A storm may form off the Atlantic coast, possibly developing into a depression. Another area southeast of Bermuda has a moderate development chance. These edge-driven storms have marked the season, forming where hot air meets cooler zones.

Global Heat Context

Reppert mentioned the U.S. heat dome’s slight contribution to August’s global record but noted that Europe experienced greater deviations from norms. “The U.S. was just a small aspect of the overall record for August,” he stated.

Relief may be on the horizon. “The intensity is expected to diminish by week’s end due to a more active northern Pacific jet stream,” Reppert said.

This summer has already set a historical precedent, with the U.S. averaging 76.9 degrees in July, breaking records since 1895. As heat domes continue to form and rebuild, the south-central U.S. has endured one of its hottest warm seasons recorded.