Overview
- A large upper-level high pressure system produced a heat dome that drove record and near-record temperatures across the south-central U.S., with NASA-modeled GEOS data showing peak warmth on Sept. 15.
- More than 41 million people were under National Weather Service extreme heat advisories, watches, or warnings as cities including Dallas, Nashville, and Memphis set daily high-temperature records.
- The dome traps sinking air that warms as it compresses while suppressing clouds, and exceptionally warm Gulf of Mexico sea-surface temperatures—reported up to about 3°C above normal—have added heat and humidity to the region.
- Short-term forecasts show a gradual cooling trend later in the week but guidance warns temperatures will remain above normal in places and a stronger cold front that could break the dome is only a developing possibility for next week.
- The event follows the warmest June–August on record for the contiguous U.S. and is straining public health systems and infrastructure through higher heat-related illness risk and extra demand on cooling and power services.