Northwest Heat Dome Breaks, But the Cooldown Could Disrupt Weekend Plans

Enjoy the heat and dry conditions while they last. Forecasters are warning that significantly cooler temperatures and rain are headed to the Pacific Northwest by the end of the week. Here is what you need to know about the major shift in the weather pattern on the way for this corner of the U.S.

Temperatures Forecast to Tumble by End of the Week in the Northwest

The Pacific Northwest has been baking under a heat dome anchored over the region since Monday. The heat is forecast to peak on Tuesday before beginning its descent on Thursday. Temperatures will reach the upper 80s and the low 90s up and down the Interstate 5 corridor stretching from Seattle to Portland. You can expect temperatures to bounce around 5 to 15 degrees above the average for the end of June. Both of these cities typically see readings in the 70s this time of the year.

The heat wave will be short-lived, as the latest forecast models signal that a major change is in store for the back half of the week. A dip in the jet stream will allow cooler air to escape from Canada and come down over the border on Thursday and Friday. High temperatures on Friday will plummet 20 to 25 degrees from where they were on Tuesday and Wednesday for much of the Northwest.

The first full weekend of summer in Seattle will feel more like the end of June, with readings expected to struggle to climb out of the 60s. For instance, the Emerald City is predicted to top out with a high of 64 degrees on Friday. Winds out of the south-southwest at 10 to 15 mph will add to the chill in the air. There is a chance that the metro area could come close to breaking the record low high temperatures for June 26, when the mercury only reached 62 degrees in 1999.

While Wednesday afternoon's World Cup game in Seattle will be a scorcher for fans, it will be a completely different situation for the match on Friday evening. Egypt is set to take on Iran at 8 pm at Seattle Stadium in the last group stage game in Seattle. Fans will want to dress in layers for the much-anticipated match. The forecast is calling for temperatures to slide into the mid to upper 50s at game time.

You will find a similar cooldown down the road in Portland. The Rose City is forecast to see temperatures fall from the mid 90s on Tuesday to readings that max out in the low to mid 60s on Saturday.

Rain Will Accompany the Chill

The arrival of a new storm system will also bring rain to the region along with the cooler temperatures. Showery conditions are expected in a zone from Washington into Oregon, Idaho, and Montana. The rain will mark the end of a two-week stretch of exceptionally dry weather. You have to go back to June 9 to find the last time that Portland recorded any rain. Seattle saw its last measurable precipitation on June 10.

The moisture machine is expected to fire up late Thursday for the Interstate 5 corridor. Portland will see rain showers make an appearance on Thursday evening. The precipitation will linger through Sunday morning. It will dry out more quickly in Seattle, with the rain expected to depart western Washington by Saturday afternoon. Although this will not be an event that packs heavy rain, the cloudy skies and light rain will mark quite the departure from the heat wave earlier in the week.

A steadier stream of moisture could develop across the interior portions of the Northwest by the weekend as the weather maker intensifies. There is even a chance that temperatures could dip low enough to support the development of snow over the top elevations of the northern Rockies.

While the rain may be an unwelcome guest for residents and tourists with outdoor plans, the moisture is good news for parts of the region that have been dealing with an elevated wildfire risk. Areas to the east of the Cascades through the northern Rockies will be under the gun for wildfire ignition and spread on Wednesday and Thursday as winds whip up ahead of the storm. Dry thunderstorms capable of generating frequent lightning strikes over the parched terrain will be the greatest concern.

The highest threat of wildfires this week will be across portions of Nevada, Utah, and Arizona. The combination of dry vegetation, gusty winds, and heat will elevate these fire hazards in the coming days.

Temperatures will return to more seasonable levels in the Northwest by the beginning of next week. For example, Portland will be back in the mid 70s by July 1. The long-range forecast models signal that it will be a beautiful Fourth of July holiday weekend across the Northwest. Stay tuned for a more precise forecast as the holiday approaches.

Weather changes fast, so help your community stay prepared. Share this story with friends, family, or your group chat, and keep your forecast in the now with Weather Forecast Now.