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Worst heat wave in 12 years coming to the Pacific Northwest

Seattle could soar to 100 degrees, a rare feat that has only happened two other times in recorded history

With California and the rest of the Southwest still reeling from the extreme heat that shattered hundreds of records last week, the Northwest is now bracing for a sweeping multi-day heat wave that could be the region's worst in 12 years.

About 13 million people were under heat alerts across Washington, Oregon, California, Nevada, Idaho and Montana on Thursday, with that number expected to grow.

A strong area of high pressure is expected to build in Western Canada this weekend, causing the jet stream to track far north and allow extremely hot air to engulf the Pacific Northwest. Temperatures are already forecast to be several degrees above average Thursday across the Northwest, and highs will only rise Friday through Tuesday. The dangerous heat will cause temperatures to soar 25-35 degrees above average, including for locations like Portland and Seattle.

Daily, monthly, and even all-time records are expected to be shattered easily. Seattle's all-time high (103), Portland's (107), and Spokane's (108) are all in jeopardy.

There have only been two past instances when Seattle was 100 degrees or hotter, and neither time was in the month of June.

The last time Portland had three days of triple digits was 2009. While they've had a handful of multi-day stretches above 100 degrees, it has never happened in June.

In addition to this being the region's worst heat wave since July 2009, it is also shaping up to be the worst June heat wave on record. Temperatures this high are more common during the late summer months.

Power grids are anticipated to be seriously strained, and worries of heat stroke among Pacific Northwest residents are growing, as a large percentage of the homes in Seattle and Portland lack air conditioning.

The heat this weekend will even impact the U.S. Olympic Team Trials for track and field. Several events like the women's 10,000 meter and men's 5,000 meter races have already been moved to earlier in the day to beat the peak afternoon heat.

The trials are being held in Eugene, Oregon where Saturday's high is predicted to be 100 degrees and Sunday's 107 degrees.

As climate change continues to elevate temperatures higher and higher, several cities across the Pacific Northwest are seeing a distinct increase in extremely hot days. Since 1970, Seattle sees eight more days per year of 85 degrees or hotter, Portland sees five more days of 90 degrees or hotter, and Boise eight more days of 100 degrees or more.