Heat waves punished the West all summer and, even at the brink of fall, another sweltering blast had moved over the region. The heat was bringing record-setting temperatures in the Southwest and exacerbating a volatile fire situation farther north.

The heat wave, which began early this week before peaking Thursday, coincided with an announcement from National Oceanic and Atmospheric Administration that the months of June through August matched the Dust Bowl summer of 1936 as the hottest on record for the Lower 48 states. “A record 18.4% of the contiguous U.S. experienced record-warm temperatures,” NOAA wrote Thursday.

This latest bout of exceptionally high temperatures was generated by a large and unusually strong zone of high pressure or heat dome parked over the Four Corners area, a situation that occurred repeatedly in recent months. Temperatures near the core of the heat dome were generally 10 to 20 degrees above average, and its influence extended everywhere west of the Central Plains.

On Thursday, record highs in the 90s and low 100s were forecast from California to Colorado; Denver and Phoenix hit at least 95 and 111 degrees, both records for the date. Excessive heat warnings were issued for parts of the desert Southwest, including Las Vegas, where the forecast high was around 105 degrees. In Death Valley, it was predicted to hit 120 degrees.

European model simulation of the heat dome parked over the U.S. Southwest. (WeatherBell)

On Tuesday, Las Vegas hit 108 degrees, tying its Sept. 7 record. Death Valley reached 122 degrees, the hottest temperature ever recorded this late in the calendar year anywhere in the world. Wednesday brought record heat to parts of Southern California; Paso Robles Airport in San Luis Obispo County soared to 106 degrees, among other records.

By Friday and especially Saturday, the heat was forecast to ease some in the West as the heat dome drifted eastward and weakened slightly. Over the weekend, the core of the heat was expected to shift into the Southern Plains.