Temperatures in much of coastal California exceeded 100 degrees Fahrenheit (38 degrees Celsius) on Friday morning, making it unbearable after midnight. Authorities warned that the extreme heat would continue into the weekend.
According to the National Weather Service, temperatures along the coasts of Santa Barbara, Ventura and Los Angeles counties ranged from just over 30 degrees Celsius to over 37 degrees Celsius at night.
Such high temperatures occur there at this time of night about once a year, said Bryan Lewis, a meteorologist with the National Weather Service in Oxnard, California, in a telephone interview.
“We’re not seeing large amounts of emissions at night,” he said, adding that temperatures elsewhere in the region remained high early Friday morning, ranging between 25 and 27 degrees in more densely populated areas. “That’s absolutely concerning.”
Heat warnings and advisories were in effect across the Western United States early Friday. Heat alerts were in effect for more than 31 million people in parts of Arizona, California, Nevada and Oregon.
An extreme heat warning is the most serious heat alert, issued when hot weather could cause illness or death if people don’t take precautions, according to the National Weather Service. Warnings in the Los Angeles area were expected to last through Monday.
Warm nights can be deadly. Studies have shown that death rates can increase by 10 to 50 percent on hot days because it is harder for people to cool down after a hot day. People who work outdoors, the elderly, young children, the sick and the homeless are particularly at risk.
In most parts of the United States, climate change has caused nighttime temperatures to warm faster than daytime temperatures, leaving fewer people spared from the heat of the day. As a result, air conditioners and other appliances have also broken down less often at night, leading to higher emissions and a higher risk of failure.
The overnight heat in California followed a day of record-breaking temperatures during a weeks-long heat wave. Burbank airport reached 46 degrees on Thursday, tying the record set once in July 2018 and twice in September 2020, the National Weather Service said.
Phoenix recorded its 100th consecutive day of temperatures of at least 100 degrees on Wednesday, and the city hit 116 degrees on Thursday – the lowest ever recorded in September. In Los Angeles, temperatures could reach 117 degrees on Friday.
Lewis said the persistent heat overnight near Santa Barbara was due to the lack of sea breezes – winds from the west that normally bring cooler ocean air inland and act as natural air conditioning. Because of a high pressure system over land, dry, hot gusts from inland were blown toward the sea instead.
This weather phenomenon is called “sundowner” winds in the Santa Barbara County area, named after the time of day they occur.
Mr Lewis urged people to drink more water than they think they need and to wear an ice pack on the neck to prevent overheating.
“It’s night right now,” he said, “so we can’t really say, ‘Stay out of the sun.'”
