As the true “dog days of summer” get underway, AccuWeather forecasters say Mother Nature is poised to crank up the thermostat across the northwestern United States and portions of southwestern Canada. Record-challenging heat is set to arrive just as many Americans prepare to celebrate Independence Day with a wide variety of outdoor activities.
High temperatures will soar to levels well above the historical average during the holiday and beyond. Intense summer heat will elevate the risk for heat-related illnesses, especially as folks host outdoor parties, head out to cool off at the pool or lake, watch brilliant fireworks displays or even participate in holiday races.
“The heat is due to a northward bulge of the jet stream that will allow a heat dome to develop over the northwestern U.S. and western British Columbia, Canada,” AccuWeather Meteorologist Nicole LoBiondo explained.
A large area of the U.S. from Northern California through Washington state will bake under intense heat for multiple days this week.
“High temperatures through at least Wednesday are setting up to run 10-20 degrees Fahrenheit above the historical average for this time of year,” said LoBiondo. “Record high temperatures will be challenged from Medford, Oregon, to the southwestern Canadian coast.”
AccuWeather forecasters say the Interstate 5 corridor will be the zone that receives some of the most intense heat from this event.
On Monday, heat advisories were in effect from parts of Northern California to south-central and northwestern Oregon, according to the National Weather Service.
For cities like Portland, Oregon, high temperatures in early July typically top out in the upper 70s to near 80. This week, 90s will be common, and the City of Roses could even flirt with its first triple-digit temperature of the year.
Record high temperatures of 97 from 1972 and 96 from 2015 are in jeopardy on Tuesday and Wednesday, respectively, in Portland.
Wednesday’s high could approach the century mark even though the city doesn’t typically record its first 100-degree day until late July.
Farther north, Seattle can also challenge its daily record high of 91 on Wednesday that was set in 2015.
“With the holiday, residents who are planning to be outside for extended periods of time should pack plenty of water and even an umbrella to provide some shade,” said LoBiondo.
As the heat builds early this week, another factor that could further worsen outdoor conditions is wildfire smoke. AccuWeather forecasters say some wildfire smoke is expected to make its return to the Northwest on Tuesday and Wednesday.
This smoke is from western Canadian wildfires, some of which were sparked earlier this year by Mother Nature’s own fireworks display: lightning.
Near-surface smoke can arrive early Tuesday in parts of Washington and shift southward into parts of Oregon and Idaho on Wednesday.
In the smokiest areas, high temperatures may not soar quite as high, given the limited nature of the sunshine. However, air quality will take a significant hit in these areas, likely reaching poor or even unhealthy levels in some spots.
In addition to the record-challenging heat in the Northwest, conditions will remain quite hot across the Southwestern states this week.
On Sunday, Phoenix experienced its highest temperature reading so far in 2023 when the mercury reached a sizzling 115.
In fact, Phoenix hasn’t recorded a high temperature below 110 since the end of June. Historical average temperatures for the city in early July hover around 107, so any measure of heat above that threshold is significant.
AccuWeather forecasters say almost no relief is on the way as temperatures in Phoenix are expected to climb above the 110-degree threshold daily through at least early next week.
It’s a similar story in Las Vegas. After Sin City set a new record for the latest date that a 100-degree reading was observed in a calendar year on Friday, the region will continue to have highs in the triple digits into next week.
Excessive heat warnings were in effect for both the Phoenix and Las Vegas areas, according to the NWS.
Produced in association with AccuWeather
Edited by Kyana Jeanin Rubinfeld and Jessi Rexroad Shull
