

Just another autumn heat wave (Photo by Juliet Bennett Rylah/LAist)

Summer is over, but it's still really hot . There's a reason that this happens every year.

Eric Boldt, who works at the National Weather Service in Oxnard, told KPCC that this annual phenomenon is caused by storms that move from the Pacific Northwest east across Middle America. These storms leave cool air in their wake, which moves into the area between the Rocky and Sierra Nevada mountain ranges, also known as the Great Basin.

This cool air nestles in the Great Basin until it overflows, then spills down the mountainsides. This compressed air speeds up as it moves through mountain passes, and as a result, heats up. This is called "compressional heating." And who is the recipient of these hot winds? That would be Southern California, where the air pressure is low. The Santa Ana winds can be explained this way.

When does it end? Well, Boldt predicts at least one more heat wave before Halloween, which is good for those of us who want to cavort around in a sexy pizza costume late at night. The rest of us will have to wait until November for cooler temperatures.