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Excessive Heat Warning

Rare June heat wave grips San Francisco as triple-digit heat stifles West

By Alex Sosnowski, AccuWeather senior meteorologist
June 13, 2019, 1:47:05 AM EDT

Golden Gate

Mother Nature cranked up the heat across the West during the first half of this week, with dozens of record highs shattered.

San Francisco was among the cities to shatter record highs as the temperature throttled to 92 F on Sunday, up to the triple-digit mark Monday and 98 F on Tuesday.

"Temperatures in San Francisco reached 100 F on Monday, which was 3 degrees higher than the maximum temperature at Las Vegas and equaled the high at Sacramento, California," according to AccuWeather Senior Meteorologist Dan Pydynowski. Monday's high beat the old daily record of 94 set back in 1994, and Tuesday's high shattered the old daily record of 88 set in 1985.

Tuesday was the third consecutive day above 90 in downtown San Francisco, a streak that's previously happened only 13 times on record and only the third time it's occurred outside of September or October.

The heat throttled back in the Bay Area on Wednesday.

Records Bay Area Monday

Coastal Central California's highs are typically within a few degrees of 70 F due to the cooling influence of sea and bay breezes off of the cool Pacific water.

Many locations in California surpassed old record highs set 25 years ago in 1994, or even earlier. Record highs were set on Sunday, Monday and Tuesday in San Bernardino and Ontario, California, to name a few.

california heat

San Bernardino, California, sizzled at 102, 104 and 109 F from Sunday through Tuesday, respectively, while the mercury registered 105, 107 and 109 in Ontario, California, from Sunday through Tuesday, respectively.

Monterey, California, which lies along the cooler waters of the Monterey Peninsula, recorded a record high of 96 on Monday, breaking the old record of 91 set back in 1994.

The high of 92 in Monterey on Tuesday shattered the old record of 78 set in 2012.

New high temperature records were set in many other cities across the state on Tuesday.

A northward bulge in the jet stream, combined with an area of high pressure, stopped the June gloom in its tracks.

The pattern created an offshore flow of dry air and pretty much stopped the traditional marine flow that creates morning low clouds and a cool afternoon sea breeze along the West coast.

When the air descends from the nearby mountains, it becomes compressed and heats up. The pattern is much more common during the late summer and autumn.

The combination of a slight offshore breeze and intense sunshine this time of the year pushed temperatures to record high levels along the coast.

The core of the heat shifted into the northwestern United States on Wednesday.

The mercury soared to 97 in Portland, Oregon, on Tuesday, breaking the old record of 95 set way back in 1941. Wednesday's high of 98 shattered the old record of 93 set in 2002.

Similarly, in Seattle, the high of 87 on Tuesday broke the old record of 84 set in 1989. The city reached 95 on Wednesday, which crushed the old record of 85 from 1999.

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As the interior Northwest sizzles on Thursday, temperatures are forecast to throttle back along the Pacific coast.

Highs in Riverside, California, are projected to trend from the upper 80s on Thursday and lower 80s by Friday.

Cali Cooling Trend Late Week

In San Francisco, after a high of 98 on Tuesday, highs are forecast to be near 70 on Thursday, which is the average high for the date.

Seattle and Portland will return to the lower to middle 70s by Friday.

Coastal Southern California has been spared the core of the heat with some interaction of the marine flow helping to moderate temperatures.

In general, the marine flow will become more prominent during the second half of this week in California. The typical June pattern will be in play at Pebble Beach Golf Links, California, for the U.S. Open.

Meanwhile, the combination of low humidity, sunshine and drying vegetation will continue to increase the risk of wildfire ignition and spread even though the core of the heat has passed.

Weather conditions and tremendous vegetative growth this spring following prolific precipitation this past winter are promoting an early fire season.

AP LA wildfire June 9

Los Angeles County firemen fight a brush fire burning close to Six Flags Magic Mountain and Hurricane Harbor amusement park in Santa Clarita, Calif., Sunday, June 9, 2019. (AP Photo/Rick McClure)

People are urged to use caution when operating power equipment and working with open flames. Never toss burning cigarettes outside of a vehicle. Avoid parking vehicles on brush as the exhaust system is hot enough to start a fire.

This past weekend, a wildfire threatened Six Flags Magic Mountain amusement park in Southern California. Several other small wildfires occurred in California on Monday, including at least two in the Bay Area of Central California, according to the Associated Press.

"An uptick in thunderstorms across the interior higher elevations late this week can elevate the risk of lightning-induced wildfires," Elliott said.

Farther north, abnormally dry to severe drought conditions have developed in part of the Northwest, according to the United States Drought Monitor.

On June 3, 2019, a blaze dubbed the 243 Command Fire began in central Washington, northeast of Yakima. The short grass and brush fire, now 85% contained, has consumed more than 20,000 acres.

Download the free AccuWeather app to see how temperatures will trend in your community. Keep checking back for updates on and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.

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