Weldon B. Johnson

The Republic | azcentral.com

This is October, right?

Phoenix broke a record Thursday when the temperature at Sky Harbor Airport reached 100 degrees just after 2:30 p.m. The previous record high for Oct. 27 was 98 degrees in 2001.

The city’s 100-degree high also set the record for the latest date reaching triple digits, according to the National Weather Service in Phoenix. The previous mark was Oct. 23, 2003.

The normal high for Oct. 27 is 84 degrees.

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The reason for the autumn heat wave is high pressure, the usual culprit for Valley heat. High pressure usually means clear skies which allows the heat of the sun to drive up temperatures.

A ridge of high pressure that is particularly strong for this time of year has lingered over the area for much of the month.

"While this might be a typical or even a slightly weaker high for July, for late October, it’s not," National Weather Service meteorologist Paul Iñiguez said. "It’s real unusual. That’s what makes the difference."

There have been 24 days with highs of at least 90 degrees this month. The record for 90-degree highs in October was set in 1952 when the temperature reached that mark on 29 days. There were 25 straight days with 90-degree highs in October 1952 compared to 23 straight days (so far) this month.

There should be some relief on the way. A weather system expected to move through California starting on Friday should bring cooler weather our way. After a high of 95 Friday, highs should drop into the upper 80s to lower 90s over the weekend and fall into the 80s early next week.

"That low should be skirting through the area (Friday), it will knock our temperatures down several degrees," Iñiguez said.