Monday is expected to the feature the Valley's coolest high temperature in more than four months.
Forecasters expect the high to reach only 84 degrees. Tuesday, meanwhile, should kick things up a couple notches with a morning low of 65 degrees and an afternoon high of 87 degrees.
“These would be the first time highs were dipping down into the 80s since May,” Austin Jamison, a meteorologist at the National Weather Service.
They also mark a mellow transition into fall, which officially started Sept. 22.
Experts say Wednesday should see a low of 66 degrees and a high of 89 degrees, while Thursday should see a low of 67 degrees and a high of 87. On Friday, the low will be back down to 65, while the high should be 86 degrees.
The last time the Valley saw highs in the 80s was May 22 when the official temperature hit 80 degrees at Sky Harbor International Airport, Jamison said.
The cooling is due to moisture coming in from Tropical Storm Olaf moving over Baja, California and a low pressure trough, also coming in from the Pacific Ocean, said Mike Paddock, a Weather Service meteorologist.
Paddock said the area has a slight chance of showers, mainly late Saturday night and early Sunday.