When dawn broke Sunday in Death Valley, Calif., the low temperature was a sweltering 107.7 degrees, the highest recorded in North America. By the late afternoon, the mercury had swelled to a blazing 128.6 degrees. The combination of the two produced the highest daily average temperature observed on the planet: 118.1 degrees.
The astonishingly hot temperatures occurred amid a punishing heat wave in the West, focused between interior Oregon, Central Valley in California, and southern Nevada. Intensified by human-caused climate change, the heat wave is fueling fast-moving wildfires and only slowly abating.
Sunday's probable world record daily average temperature of 118.1 degrees was registered at the Stovepipe Wells weather station in the northern part of Death Valley National Park. It is separate from the more frequently referenced temperature measurements at Death Valley's Furnace Creek, located about 18 miles to the southeast. Furnace Creek is home to the highest maximum temperature recorded on the planet: 134 degrees, set July 10, 1913.
Sunday morning's low of 107.7 degrees at Stovepipe Wells marked the second highest minimum temperature observed worldwide, only trailing the coastal city of Quriyat, Oman, which never dropped below 108.7 degrees on June 26, 2018.
The afternoon high that day in Stovepipe Wells of 128.6 was its highest on record (since 2004). It was actually hotter in Furnace Creek on Friday and Saturday, where the temperature soared to 130 and 129.4 degrees, but somewhat lower minimum temperatures resulted in less searing averages compared with Stovepipe Wells. (Low temperatures at Furnace Creek on Friday and Saturday were 104 and 99 compared with Stovepipe Wells's 108 on Sunday.)
News of Sunday's record-setting average temperature at Stovepipe Wells was first posted on Twitter by Thierry Goose, who monitors internal weather data from Canada, and corroborated by both Maximiliano Herrera, an expert on world weather extremes and Etienne Kapikian, a forecaster with Meteo France.
While any significant record-setting temperatures in Death Valley since Friday are preliminary and require validation from the World Meteorological Organization, the measurements at Stovepipe Wells are probably legitimate as they were produced from the U.S. Climate Reference Network, considered the gold standard for weather observation. The network relies on high quality instruments which monitor weather in stable, undisturbed locations, according to the National Oceanic Atmospheric Administration. Temperatures are computed based on the output of three independent thermometers.
The record-setting 24 hours in Stovepipe Wells on Sunday capped a blistering three-day stretch in Death Valley, which began with the 130-degree high at Furnace Creek on Friday. It equaled the 130-degree mark set in August in Furnace Creek and, if confirmed, would mark the planet's highest temperature since at least 1931.
Only two other known measurements have been higher: The 134-degree reading from Furnace Creek in 1913, and a 131-degree reading from Kebili, Tunisia, set July 7, 1931.
But Christopher Burt, an expert on world weather extremes, questions the legitimacy of both of those measurements. He called the 1913 Furnace Creek reading "essentially not possible from a meteorological perspective" and wrote that the 1931 Tunisia reading has "serious credibility issues."
In other words, the 130-degree readings set at Furnace Creek both Friday and last year, if validated, may be the highest pair of reliably measured temperatures observed on Earth.
Even if you accept the 1913 high temperature, the daily average temperatures this year and last year at Furnace Creek are hotter because of much higher minimum temperatures. On Friday, when the high was 130 in Furnace Creek, the low was 104. But in 1913, when the high was reportedly 134, the low was a much milder 85.
The exceptionally high temperatures in Furnace Creek have also been notable for their longevity. They reached 126 on Wednesday and Thursday, before peaking at 130 on Friday. On Saturday and Sunday, they climbed to 129.4 and 127.9. Monday's forecast again calls for highs to reach the high 120s. The low in Furnace Creek hasn't fallen below 99 degrees since Tuesday.
The hot and exceptionally dry weather has created tinderbox conditions for the rapid spread of wildfires. According to the National Interagency Fire Center, 59 large blazes are burning in a dozen states, 11 of them in California and Oregon. Smoke from wildfires in the West and British Columbia spread over "most of the western half of the U.S.," according to the National Weather Service.
As of early Monday, the Bootleg Fire in southwest Oregon had burned more than 153,000 acres, the blaze doubling in size daily between Friday and Sunday.
The fire had made electricity transmission into California unreliable, and the state's grid operator urged consumers to conserve energy on Monday.
Temperatures on Monday and Tuesday will remain above normal in the Southwest and California's Central Valley but will back off gradually from record-setting territory.
Toward the middle of the week, the heat dome, or zone of high pressure responsible for the sweltering temperatures, is forecast to weaken while the summer monsoon strengthens. This will bring some much-needed rain in Arizona, New Mexico, Nevada and western Colorado, all of which are enduring extreme to exceptional drought conditions.
However, long-range computer models show potential for another intense heat wave in the West building by next weekend, focused on the central and northern Rockies, which could bring more exceptionally high temperatures.
The heat wave afflicting the West is the third in just over three weeks, after the “unprecedented” Pacific Northwest event at the end of June. and a record-setting blast in the Southwest in the middle of the month; together, they vaulted the nation to its hottest June on record. The heat wave in the Pacific Northwest was made at least 150 times as likely by human-caused climate change, according to a panel of scientists.