Summerlike heat to fade for western U.S.

After nearly a full week of oppressive summerlike heat for the western United States, temperatures will finally ease back to normal levels this week.

As of Saturday, the sting of summerlike heat had already begun to fade for many coastal cities and areas immediately inland. Downtown Los Angeles, for example, reached a high temperature of 79 Fahrenheit on Saturday, full 10 degrees lower than Friday's high of 89.

However, heat refused to release its grip on cities farther inland, into the valleys and deserts of California, and portions of the Southwest where record heat continued.

In California, Bishop, Montague and Mt. Shasta City all set record-high temperatures on Saturday, reaching 94, 92 and 86 respectively. These records were last set in 1960, 1987 and 1969 respectively.

Farther east, Reno, Nev., reached a high of 88, breaking the previous record from 2001. And in Arizona, Phoenix recorded its fifth day in a row of over 100-degree heat.

Thankfully, AccuWeather meteorologists say the end of this record-breaking heat wave is on the horizon.

Mid the coronavirus pandemis, Beaches are now open with many restrictions in Orange, Ventura, San Diego and Santa Barbara counties. Los Angeles County officials say they may begin gradually reopening beaches as soon as Wednesday. Gov. Gavin Newsom's stay-at-home order remains in place.

The persistent upper-level atmospheric pattern that has locked summerlike heat into the West and record-breaking cold into the East will finally begin to break down on Sunday, allowing a storm system to develop off the coast of California.

This storm will advance toward the West Coast on Monday, ushering in some much-needed rainfall to Northern California and Oregon. Ahead of this system, wind direction over much of California will shift, which will allow temperatures across the region to regulate.

"As the offshore winds begin to subside, cooler conditions will return to much of California finally," AccuWeather Meteorologist Courtney Spamer said.

During this heat wave, much of the state has been dominated by hot offshore flow. Winds will continue to shift across the region on Sunday and more of the West Coast will be placed under the influence of cooler onshore flow.

Some coastal locations have already experienced the temperature relief onshore flow can bring.

San Francisco received quite the temperature shock from Friday to Saturday when winds shifted. On Friday, under offshore winds, the city reached a high of 82. While under the influence of onshore winds on Saturday, the mercury was unable to surpass 66.

Conditions will begin to cool off in earnest for much of California on Sunday, with many locations recording temperatures 5-10 degrees lower than Saturday.

Coastal communities will remain in the 60s on Sunday, while areas just inland reach into the 70s. Valley locations will remain rather warm on Sunday with temperatures in the upper 80s to lower 90s expected. Desert locations will remain under triple-digit heat.

As the storm comes ashore Monday afternoon and spreads showers over Northern California, temperatures will trend even lower across the state. Many locations such as Sacramento, Calif., and downtown Los Angeles are forecast to reach temperatures very close to average for this time of the year.

Even lower temperatures are expected for Tuesday before conditions plateau on Wednesday. By Tuesday, locations across the state of California will be around 20 degrees cooler than their hottest day of the past week.

Coastal communities dip into the upper 50s to lower 60s on Tuesday and Wednesday, while inland areas sag into the low to middle 70s. The typically hotter valley and desert locations will not miss out on the cooldown as temperatures are forecast to reach the upper 70s and upper 80s to low 90s respectively.

"The drop in temperatures is likely to make it easier for residents to find ways to more comfortably social distance outdoors amid the COVID-19 lockdown across the state," Spamer said.

While relief from summerlike heat in California will begin as the weekend concludes, those hoping for cooler conditions in the Desert Southwest will have to hold on a bit longer.

Cities like Phoenix will continue to flirt with triple-digit heat through Monday, before more seasonable temperatures in the lower 90s are forecast to arrive on Tuesday.