Western Heat Wave Enters Second Chapter; More Record Highs Through Holiday Weekend (FORECAST)

Jon Erdman
Published: July 2,2015

While it may not be quite as hot as this past weekend in some areas, there appears to be no end in sight to this torrid heat wave in the West.
June and even a few all-time record highs have already been shattered in parts of the interior Northwest, northern Rockies and Great Basin. The extreme heat is likely to last into next week and may end up breaking records for longevity as well.
(MORE: Northwest Heat Wave By the Numbers)

The upper-atmospheric setup for the Northwest heat wave this week.

Through the holiday weekend, daily record high temperatures will likely be threatened in some cities. Medford, Oregon, tied its daily record on Wednesday (108 degrees). Eugene, Oregon, set daily record highs both Wednesday (99 degrees) and Thursday (101 degrees). Seattle also set a daily record high on Thursday by topping out at 93 degrees.
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 holiday weekend, but overall it will remain a dominant feature.
This will allow the sizzling early-July sun to send temperatures soaring in the Pacific Northwest, northern California, interior Northwest and northern Rockies.

Hot Into Next Week

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

Current Temperatures

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. Temperatures will surge towards the middle 100s through the holiday weekend.
(FORECASTS: Seattle | Portland | Boise | Salt Lake City)
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.
This heat appears to be locked in place well into next week, though perhaps somewhat muted compared to the magnitude of the heat we've seen so far.
(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 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 upper 80s to low 90s through the holiday weekend and likely into next week. On average, they typically see the 90-degree mark only three days a year. They've seen three days in the 90s from this heat wave through Thursday. 
• Portland, Oregon last saw triple-digit heat in August 2012. They could approach the 100s this weekend. The city may also make a run at its longest streak of 90-degree days; that was a 10-day streak in 2009. Through Thursday they had recorded four days in a row with highs in the 90s.
• Medford, Oregon may see triple-digit highs every day through the holiday weekend, if not longer.
• Salt Lake City Six days a year reach 100-degrees or hotter in the Salt Lake Valley, on average, and as of Wednesday there have been four days. Temperatures are forecast to be near 100 degrees into this weekend.

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.
(MORE: Earth's Record Year? | How Hot is Too Hot?)
Meteorologist Chris Dolce contributed to this report.

MORE: Heat Waves of the Past (PHOTOS)