On This Day: The 1955 Los Angeles Heat Wave | WeatherBug
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On This Day: The 1955 Los Angeles Heat Wave

August 31, 2021
UPDATED By WeatherBug Meteorologist, Andrew Rosenthal
September is often the hottest month of the year in southern California and last year the records were re-set as temperatures across the Southland soared as high as 121 degrees. While brief heat waves aren’t uncommon across the Southwest in September, prior to 2020 the standard-bearer was a scorcher that hit the region 65 years earlier in 1955.
 
Why is September such a sizzling time in greater Los Angeles? The weather often gets stuck in a pattern that favors extreme heat. By September, cooler Canadian air is able to make inroads from the Canadian Prairies into the Upper Midwest and eastward. This, in turn can cause an upper-level heat ridge to bulge into the Great Basin, leading to winds shifting offshore and cutting off the cooler marine air that can keep temperatures in check. With the high pressure producing sunshine and repetitively hot days, the mercury can soar past the century mark, evenn across the valleys.
 
Such was the case in 1955, when a heat wave made its presence felt in the City of Angels starting on August 31. The peak of the heat was felt on September 1st, as temperatures climbed as high as 109 degrees, tying the all-time record set some 64 years prior. Far from being over, the heat continued for the next week without highs falling out of the triple digits. Even the beaches offered little in the way of relief, with temperatures near or above 90 degrees in coastal Santa Monica and Oxnard, Calif. It finally took until September 7 before the mercury dropped back into the 90s and then closer to seasonal normals in the 80s.
 
Ironically, residents of southern California initially cheered the weather pattern. The typical onshore flow pattern into Los Angeles trapped heaps of smog in the air for six days in late August. The turning of the winds to be offshore meant that the smog was able to clear out and breathing was a bit easier.
 
However, as the heat wave pressed on, the consequences became devastating. Much of what is now suburbs outside Los Angeles proper was farmland at the time. The heat led to a mass die-off of chickens, particularly egg-laying hens. By some reports, as many as 11,000 chickens were dying each day from the heat.
 
Of course, chickens weren’t the only ones affected by the heat. Each successive day of hot weather was followed by an increase in deaths among residents. With deaths at 2 to 3 times their normal rates among those in their 50s and as much as 8 times normal for elderly residents, mortuaries were overwhelmed.
 
By the time the heat ceased, 946 people were dead. This remains one of California’s deadliest natural disasters, second only to the 1906 San Francisco earthquake, which was responsible for an estimated 3,000 to 6,000 deaths.