An unusually late heatwave has been forecasted for the southwestern United States, including California and Arizona. On September 3rd, the National Weather Service (NWS) issued an Excessive Heat Warning for a broad region extending from California's Central Valley east of San Francisco, across the western coastline, southern Nevada, and southwestern Arizona. The heatwave is expected to impact major southwestern cities, including the densely populated areas of the San Francisco Bay Area, Los Angeles (LA), as well as San Diego, Las Vegas, and Phoenix. According to the Los Angeles Times, temperatures in downtown LA are projected to reach between 35°C and 40°C this week, with the San Fernando Valley in Southern California possibly approaching 43°C. Los Angeles Mayor Karen Bass announced that hundreds of cooling centers will be operational citywide from this morning through September 6th.

Los Angeles, known for its mild and warm climate with an average annual temperature of around 20°C, typically experiences temperatures in the low 30s°C even during its hottest month, August. However, according to the Associated Press, Arizona is facing an exceptionally high-temperature period this year, although this time of year is generally hot. On September 3rd, Phoenix, Arizona, set a new record by reaching temperatures above 37°C for 100 consecutive days, surpassing the previous record of 76 days set in 1993. Meteorologists attribute the unusual heatwave in the southwestern United States to a mass of hot air trapped in the upper atmosphere, which is suppressing the cooler Pacific air. Rich Band, a meteorologist with the National Weather Service (NWS), told Reuters, “The strong high pressure is preventing the development of clouds, cool winds, showers, or thunderstorms that could counterbalance the solar radiation and heat in the southwestern region.”

(The Chosun Daily 2024.09.04)