Phoenix Ties All-Time August Heat Record as Southwest Sizzles; Heat Relief Arrives in Northwest

Nick Wiltgen
Published: August 15,2015




 
When the National Weather Service issues "excessive heat warnings" for the hottest region of the country, you know it's hot. And when Phoenix ties its all-time August record high, you know it's really hot.
Excessive heat warnings remain in place for more than 14 million Americans in three states, as the bubble of high pressure responsible for the recent heat wave in Texas and Louisiana shifts westward to Arizona, putting the Desert Southwest in the hot seat.
And it's not just the Southwest that's feeling the heat. The Northwest and northern Rockies have also been baking lately. But while relief has begun to move in there, that relief is creating problems of its own in the form of strong winds and the threat of lightning strikes – and those raise the danger of wildfires, both new and existing.

Southwest: August Records Challenged

Southwest Heat Setup

At least one major heat record has already been established in this heat wave. On Friday, Phoenix Sky Harbor International Airport recorded a high of 117 degrees, tying the Arizona capital's all-time record high for the month of August previously set Aug. 26, 2011. Like that date, Friday's low was 93, so it also tied for Phoenix's warmest daily mean temperature on record for the month of August.
(FORECAST: Phoenix | Scottsdale | Mesa)
In a way, to call this a "pressure cooker" could be considered more than just a metaphor. The high-pressure zone is literally exerting a downward influence on the air over the Southwest. Since clouds and rainfall require rising air motions (not to mention adequate moisture), large-scale sinking air tends to prevent or inhibit precipitation from developing.
That means more sunshine, which in turn, means more heat. In addition, the air mass itself is warmer in the first place, so the sun is heating up air that's already toasty to start with.
Relative to historical norms, the epicenter of the heat will remain over central and southern Arizona through the weekend.

Three-Day Forecast

Phoenix's 117-degree high Friday made it the hottest day of 2015, surpassing the 115 recorded June 18. Of the past 20 years (1995 through 2014), Phoenix's annual high temperature has only occurred in August three times: 2012, 2004 and 1999. In 2004 and 1999 August shared the crown with July.

Current Temperatures

The National Weather Service continues excessive heat warnings for most of Arizona's lower elevations, along with the lower elevations of the Las Vegas area, the low deserts of southern California, and even into the mountains and inland valleys around Los Angeles and San Diego. If you are in any of these areas, take precautions against the heat. Drink plenty of water, stay in the shade as much as possible, and take a break now and then in an air-conditioned building.
At least twelve daily record highs were broken on Saturday with six additional locations tying their record highs for today's date.
(FORECAST: Tucson | Las Vegas | San Diego)

Southern California Temperatures

In Los Angeles, highs are likely to soar well into the 100s in the San Fernando Valley, even as the city's westside beaches enjoy comparatively mild temperatures stopping in the lower 80s. The Weather Channel smartphone app and weather.com give you forecasts down to neighborhood and zip-code level, so make sure you check the forecast for your specific area of interest to get the forecast most relevant to your plans.
(FORECAST: Downtown L.A. | LAX Airport | Encino)

Northwest: Fire Danger Shifts East Ahead of Cooler Air

A cold front has swept through the Northwest and has knocked down the heat in that region.
(FORECAST: Seattle | Portland | Boise)
Unfortunately, this friendly front brought along some bad company – a punch of strong winds in the middle and upper levels of the atmosphere. Some of that wind momentum continues to accompany that front into Montana, where windy conditions will create high wildfire danger Saturday. Any existing wildfires will be difficult to control during the windy conditions.
(MORE: Latest on Western Wildfires)

Current Fire Weather Alerts

On top of that, the front will continue to set off some thunderstorms, and any lightning strikes from those storms could set new fires, particularly where lightning bolts land outside the rain footprint of their parent thunderclouds.

Current Fire Weather Conditions

While the wildfire danger is unwelcome, the cold front will sweep the broiling heat out of the region for a little while. Cooler air with reduced fire threats are expected across the Northwest and northern Rockies for the day on Sunday.
(FORECAST: Billings | Casper)
MORE: Western Wildfires, July 31 - Aug. 11, 2015