Record Western Heatwave

Jon Erdman and Chris Dolce of the Weather Underground has provided a blog on the ongoing Western U.S. Heatwave

Western Heat Wave Enters History Books; At Least 16 June Record Highs Already Broken (FORECAST)

Jon Erdman 
Published: June 29, 2015

A torrid heat wave has shifted into high gear and has already broken June record highs in at least 16 cities in the Northwest, two of which appear to have tied their all-time record highs. The extreme heat is likely to last well into early July and may end up breaking records for longevity as well.

New Record Highs Set

According to the National Weather Service, at least six locations in Washington state appear to have topped their all-time June record highs on Sunday. 

An unofficial weather station located in Hell's Canyon along the Oregon/Idaho border (Pittsburg Landing) recorded an incredible 116 degrees for a high Sunday. 

The culprit in this hot setup is a dome of high pressure aloft, surging northwestward to encompass a large area of the western states. The center of this high will shift around through the week ahead, but overall it will remain a dominant feature.

This will allow the sizzling late-June and early-July sun to send temperatures soaring not simply in the typically hot Desert Southwest, but also locations well to the north including the Pacific Northwest, interior Northwest and northern Rockies. 

Hot Week Ahead

Highs well into the 90s and triple digits are expected in many lower-elevation locations west of the Continental Divide and inland from the Pacific Coast.

Heat Alerts

This includes much of Nevada, California's Central Valley, the Salt Lake Valley, Idaho's Snake River Plain, much of Oregon's lower elevations east of the immediate coast, and areas to the east of the Cascades in Washington State.

In particular, parts of the Columbia Basin and lower Snake River Valley will see particularly extreme and persistent heat. This includes cities such as Yakima, Kennewick and Walla Walla in Washington as well as Lewiston, Idaho, as noted in the records above. Temperatures will get knocked down a bit into the low 100s to start the new workweek, but will then surge towards the middle or upper 100s again late in the week.

(FORECASTS: Seattle | Portland | Boise | Salt Lake City)

The extreme heat has even surged north into Canada. Cranbrook, in far southeast British Columbia at an elevation of about 3,000 feet, set a new all-time record high of 98 degrees (36.8 degrees Celsius) Sunday, according to The Weather Network. 

Even Revelstoke, British Columbia – 130 miles north of the U.S. border, about 1,500 feet above sea level and better known for skiing – reached an amazing 103 degrees (39.5 degrees Celsius) Sunday.

Current Temperatures

Compared to what the more arid Great Basin is used to, evening and overnight temperatures will be slow to drop, bottoming out in the 70s in the hottest locations.

In that regard, the air mass moving north into the region already has a strong pedigree; Las Vegas recorded a low of 91 on Friday, marking the first time Vegas has ever recorded a daily low in the 90s during the month of June. This happened again Sunday, when the calendar-day low was only 90 degrees. (The previous record-warm daily low in June was 89 on June 29-30, 2003.)

Saturday morning's low at Portland International Airport was 71 degrees. This is the first time PDX has ever recorded a low in the 70s in the month of June.

Wenatchee, Washington, set a June record warm low temperature Sunday, only dipping to 77 degrees. The old June record warm-low temperature, there, was 75 degrees on June 30, 1998.

This heat appears to be locked in place well into the week ahead, as the upper-level dome of high pressure remains camped out near the Great Basin. In fact, many interior Northwest locations may see highs in the 100s every day from now through at least July 10.

(MAPS: 10-Day Temperature Forecasts)

Forecast Highs

The hot, dry weather is also causing a high fire danger, as drought conditions have worsened over the Northwest and northern Rockies in the spring. Disturbances riding around the west side of the upper-level ridge and just enough mid-level moisture may trigger isolated, mainly dry afternoon thunderstorms, which may ignite new wildfires. 

(MORE: Wenatchee, Washington Wildfire)

In mid-May, Washington Gov. Jay Inslee issued a statewide drought emergency, and spring runoff from winter's paltry snowpack was expected to be the least in 64 years. 

Seattle has seen only 8 days with measurable rain since May 1, one-third the average number of such days, according to NWS-Seattle. Portland, Oregon, set a new record June dry streak of 24 straight days through Saturday, according to NWS-Portland. 

One of the biggest factors in heat wave deaths is not only the magnitude, but also the longevity of the heat. 

• Seattle will see highs in the middle 80s to low 90s through the week ahead. They reached the low 90s on Saturday and may see several more days in the low 90s later this week. On average, they typically see the 90-degree mark only three days a year. 
• Spokane, Washington may see a couple of days with century-mark highs through next weekend. Only one such day a year is the average, there. Even when not in the 100s it will be at least in the middle or upper 90s.
• Portland, Oregon last saw triple-digit heat in August 2012. They may see at least one, if not more in this heat wave late this coming week. The city may also make a run at its longest streak of 90-degree days; that was a 10-day streak in 2009.
• Medford, Oregon may tie its record number of June triple-digit days (6 days in 1987, 1970 and 1926) and will likely tie its June record for 90-degree-plus days (21 in 1918).
• Salt Lake City may see triple-digit highs several days into next weekend. Six days a year reach 100-degrees or hotter in the Salt Lake Valley, on average and as of Monday there have been three days.

Epicenter of the Heat

This is a dangerous heat wave. Take safety precautions against the heat.

Those playing or working outdoors, as well as those without access to air conditioning, will face an elevated risk of heat-related illness. According to the U.S. Energy Information Administration, 25 percent of homes, apartments, condos in the states of Idaho, Montana, Utah and Wyoming do not have air conditioning. 

Remember to never leave kids or pets unattended in cars and drink more water than usual. Wear light-colored clothing and keep your head and body cooler with a hat. Take frequent rest breaks in shaded or air-conditioned environments.

New Record Highs

Here is a rundown of the June record highs tied or broken Sunday:

• Walla Walla, Washington, hit 113 degrees. According to Weather Underground weather historian Christopher Burt, if validated this reading will establish a new June record high not just for Walla Walla, but the entire state of Washington. That record is 112 degrees at John Day Dam on June 18, 1961. Of course, Sunday's high also crushed the June record of 109 set just a day earlier, which in turn beat the record of 107 set June 23, 1992.
• Lewiston, Idaho, reached 111 degrees. This broke the previous June high of 109 set on June 22, 1936. Burt says this too may be a new June record for the state of Idaho, surpassing the 110 degrees recorded at six different locations.
• Boise, Idaho, topped out at 110 degrees. This replaced the previous June high of 109 set June 19, 1940. It also missed Boise's all-time record high by 1 degree, and was the hottest day in Boise since a high of 110 on Aug. 4, 1961.
• Ephrata, Washington, hit 110 degrees to break the record of 107 set Saturday. Previously 106 was the June record from June 30, 1998. Sunday goes down as the second-hottest day on record in Ephrata behind the 115 recorded Aug. 4, 1961.
• Pendleton, Oregon, topped out at 109 degrees both Saturday and Sunday. Those readings broke the city's all-time June record high of 108 set June 30, 1924, and June 17, 1961. June records in Pendleton go back to 1893.
• Yakima, Washington, reached 108 degrees both Saturday and Sunday. Those broke the previous June high of 105 set June 23, 1992, and just tied earlier in June. Official National Weather Service records for Yakima go as far back as 1946.
• Spokane, Washington, hit 105 degrees Sunday. That broke a record that had only stood for one day – 102 degrees on Saturday. Before this heat wave the June record had been 101 on June 23, 1992; records in Spokane go all the way back to 1881, making this an especially impressive record. Sunday was also the hottest day in Spokane since Aug. 4, 1961.
• Kalispell, Montana, hit 102 degrees to crush its June record of 97 degrees just set Saturday. The previous June record was 96 set June 22, 1955, and the previous record for earliest 100-degree day was July 6 back in 2007. Temperature records there began in 1899.
• Missoula, Montana, saw a high of 102 degrees. This breaks the previous June record high of 101 set Saturday, and marks the first consecutive triple-digit June days, there. Prior to that the June high had been 100 on June 29, 1937 and June 13, 1918. Records date back to 1893.
• Meacham, Oregon, hit 101 degrees Sunday to set its third consecutive June record high. Saturday's high was 98; Friday's 93 had tied the old record of 93 from June 16, 1961. Sunday's high also beat the daily record for June 28 by a whopping 16 degrees.

Gerard Tangalan Of Seattle leans on International Fountain while cooling off at the Seattle Center July 29, 2009 in Seattle, Washington.
(Stephen Brashear/Getty Images)

The following record highs for the month of June were broken on Friday and Saturday, not including cities that matched or broke them again Sunday:

• Burns, Oregon, reached 102 degrees Saturday to break its June record of 100 set June 29, 2008, and June 30, 2013. Records in Burns go back to 1939.
• Helena, Montana topped out at 103 degrees Saturday, beating its previous June record high of 102 degrees set in 1900. Records date back to 1880.
• Redmond, Oregon, had a high of 101 degrees Friday to tie the all-time June record originally set there on June 25, 1968.
• The Dalles, Oregon, tied its June record high Friday when Columbia Gorge Regional Airport, technically across the river inWashington, hit 108 degrees to match the mark set June 22, 1992.

On Monday, new daily record highs were set in Helena, Montana (100 degrees), Idaho Falls, Idaho (101 degrees), and Montague, California (99 degrees).

On Friday, new daily record highs were set in Yakima, Washington (104), Pendleton, Oregon (104), Walla Walla, Washington(105), Medford, Oregon (107), Helena, Montana (98), Eugene, Oregon (98) and Mount Shasta City, California (99). Daily record highs were tied in Seattle (87), Red Bluff, California (108), and Reno, Nevada (100).

Unofficial state-by-state highs Friday included 110 degrees at Grants Pass, Oregon; 109 degrees in Entiat, Washington; 105 degrees in Lowell, Idaho; and 101 degrees at the airport in Plains, Montana, in the far western part of that state.

Daily record highs were tied Thursday in Ely, Nevada (95), South Lake Tahoe, California (90), Olympia, Washington (90), and Bellingham, Washington (83).

(MORE: Earth's Record Year? | How Hot is Too Hot?)

June has already been a hot month in parts of the West.

Medford, Oregon, is pacing for their hottest June on record, dating to 1911. Portland, Oregon, logged its seventh day of 90-degree-plus heat this month on Saturday, breaking the June record of six days set in 2003. Earlier in the month, Yakima,Washington, had tied its all-time June high of 105 degrees. This occurred 15 days earlier on the calendar than the previous June 105-degree high. This record was then beaten on Saturday.

Meteorologist Chris Dolce contributed to this report.