Dangerous Heat Wave Building in U.S. West Could Break Records

The U.S. West is entering a dangerous and potentially record-breaking heat wave that is expected to last through Labor Day weekend. 

The temperature spike — which could push the mercury as high as 115 degrees Fahrenheit in Southern California, Sacramento and the San Joaquin Valley during the long weekend, according to The Guardian — comes amidst a summer of exceptional heat in the U.S., Europe and China. The climate crisis makes heat waves more frequent and extreme.  

“VERY DANGEROUS HEAT RISK will impact portions of interior #NorCal this Labor Day Weekend,” the National Weather Service (NWS) Sacramento warned on Twitter Monday. “The entire population is at risk.”

More than 55 million people and 20 of the most populated Western cities were under heat alerts between Southern California and the Northwest, CNN reported Tuesday. The immediate cause of the building Western heat wave is a high pressure ridge that will force the jet stream north and increase temperatures throughout the week, AccuWeather reported. This is ending a period of relief for the Desert Southwest, with Phoenix, Albuquerque, New Mexico and Las Vegas all experiencing below-average temperatures this August because of frequent rain. The new high pressure ridge will keep the rain away, and the Desert Southwest and parts of California are set to see the highest temperatures. Death Valley, California, could break September records and reach 125 degrees Fahrenheit, according to Axios. 

Heat waves are a major public health risk–the deadliest extreme weather event in the U.S. each year on average — and this one has three characteristics that concern forecasters.

“This will result in very dangerous heat given 1) extreme afternoon highs, 2) oppressive overnight lows and 3) long duration heat,” NWS Sacramento said in an online discussion reported by Axios. 

Overall, the heat wave could break more than 100 records in the West, CNN reported, but it could be deadly even if those records don’t fall.

“Some records may be broken but record max temps are very high at this time of the year,” NWS Los Angeles said in a statement reported by CNN. “Record breaking or not, this prolonged heat wave is going to be very dangerous.”

Los Angeles is one of the cities that has opened cooling centers for residents who need to escape the heat, Axios reported.

Further north, temperatures will be less extreme but unseasonable for the region. Portland and Seattle both broke daily temperature records with highs of 100 degrees Fahrenheit and 90 degrees Fahrenheit respectively, according to AccuWeather. The Portland temperature was more than 15 degrees above the city’s usual temperature for this time of year. In Boise, Idaho, the average for August could end up at 80 degrees Fahrenheit, which is the highest since record keeping began, according to The Guardian. 

While these chart-topping temperatures are cooler than the triple-digits predicted farther south, the northern states are also less equipped to weather them.

“Most buildings in these Northwest cities do not have air conditioning that can handle these waves of heat. As we’ve seen from recent events, this will make the risk for heat-related illnesses and deaths much greater,” AccuWeather senior meteorologist Mike LeSeney said on his home website. 

The high temperatures also increase wildfire risk. Oregon Governor Kate Brown even declared a state of emergency Sunday in preparation for “imminent” fires, The Guardian reported.

“It is imperative that we act now to prevent further loss — of life, property, business, and our natural resources,” she said.