Tuesday's World Series baseball game in the Dodgers' Stadium in Los Angeles broke all records for heat.
It was played at around 40 Celsius, which makes it the hottest game at any venue since the series began in 1903.
The US National Weather Service reported that there has been "another record-breaking hot day across southwest California on Tuesday, with nine records broken, including Downtown Los Angeles which broke a 108-year-old record when they reached 42 degrees".
As noted by Weather Underground, (WU), a late-year heat wave really got going on Monday and continued from Santa Barbara through Los Angeles to San Diego. In Orange County, the city of Fullerton soared to 41.7C on Monday. According to WU weather historian Christopher Burt, this is likely the highest single temperature recorded anywhere in the United States so late in the year.
Another impressive mark was made in downtown Los Angeles (the University of Southern California campus) where the thermometer hit 39C. Prior to Monday, the downtown station had never topped 38C after October 17, in records going all the way back to 1877.
The heat wave and causative Santa Ana winds are being created by a large, near-record-strength dome of high pressure that has settled in over the Great Basin, a few hundred kilometres northeast of Los Angeles. The difference in air pressure between this high-pressure system and lower pressure over Southern California has driven gusty northeast winds over Southern California.
Since these winds originated over desert areas, they are hot and dry. A red flag warning (fire danger) has been issued by the National Weather Service, stating that "this event is especially concerning because of the multiple day nature of it, which we have not seen yet this season, and such events have a history of large fires".
The average temperature in LA in October is 24C, a figure that will not be revisited until the end of the weekend.