Heat index values greater than 115F for parts of Arizona and southern California

Sep 09, 2026

Hi everyone, I have been traveling today but wanted to get out a short post this afternoon just to share an update about the ongoing heat in the country. As we have been discussing, an unusually strong area of high pressure has built across the southern half of the country at middle and upper levels of the atmosphere.

This is supporting widespread above normal temperatures across the country, with the Northwest and New England the primary exceptions.

The south central part of the country continues to be the focus for record heat, as numerous daily record were set across this area both yesterday and this afternoon. Oklahoma City hit 103F both days for new daily records each day. The overnight low for today of 77F would also tie a daily record warm minimum (assuming the temperature does not get below 77F before midnight) — and yields a daily average temperature of 90F, the third latest date on record for a daily mean temperature of 90F or warmer.

Warm overnight low temperatures are a function of both unusually warm air and high levels of moisture — and that combination is also being found in the Southwest US. As the area of high pressure providing record heat has built across the area, residual tropical moisture that moved into the area from offshore hurricane Marie has remained trapped across the area. This has resulted in an unusual combination of heat and humidity for parts of California and Arizona, with heat index values exceeding 115F in some locales. Palm Springs was reporting a temperature of 106F and a dewpoint of 72F at 2:30 pm PT, yielding a heat index of 117F. Even a location closer to the coast like Fullerton had a temperatures of 108F and a dewpoint of 63F, giving a heat index of 111F.

The warmth will continue for much of the country into Thursday — although a zone from parts of Kansas and Oklahoma northeast into the Ohio Valley will see a day of reprieve as clouds and showers/storms will help keep temperatures in check.