Thick, relentless wildfire smoke leaves Seattle, Portland with worst air quality in the world

In the Seattle area, air quality measurements ranged from the Unhealthy to Very Unhealthy categories with several sensors in the city's eastern suburbs measuring downright hazardous levels of smoke particulate.

SEATTLE Never before has a sunny and 65-degree day been so uninviting to be outdoors.

Thick wildfire smoke that has been draped over parts of the Pacific Northwest for weeks due to relentless fires burning in the Cascades and eastern Washington has become even worse over the Seattle and Portland metro areas, not only rating as the region's worst air quality of the year, but rating as the worst air quality measured anywhere in the world.

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In the Seattle area, air quality measurements ranged from the Unhealthy to Very Unhealthy categories with several sensors in the city's eastern suburbs measuring downright hazardous levels of smoke particulate. 

THE AIR QUALITY INDEX EXPLAINED

The site IQAir ranked Seattle and Portland as the two worst cities in the world for air quality on Wednesday and Thursday – worse than areas in China and southeastern Asia that usually top the list. Vancouver, British Columbia, in Canada rated among the 10 worst cities.  

HOW TO WATCH FOX WEATHER

Air quality alerts are in effect for roughly 8.3 million people through Thursday night and Friday across Oregon and Washington's Interstate 5 corridor, which includes the Seattle and Portland areas. 

Health officials are stressing for residents to stay indoors when possible and limit all outdoor activity, especially strenuous activity. And even indoor activities should remain "light." Some schools in the Seattle area have either restricted or canceled outdoor after-school sports and activities or moved them indoors when possible.

SIGNS THAT POOR AIR QUALITY COULD BE AFFECTING YOUR PET

The wildfire smoke comes amid the region locked in a historic dry stretch. Most areas west of the Cascades have received around or less than a half-inch of rainfall since the start of summer. Seattle's 0.54 inches measured since mid-June is the driest 120-day stretch of weather in its recorded history.

Relief from the wildfire smoke is on the way

But cleaner air – and everything else – is coming soon.

A major shift in the weather pattern starting Friday will usher in an extended wetter and cooler pattern across the region, not only cleaning out the smoke but dropping a significant amount of rainfall to help douse the stubborn wildfires.

FALL FLIP-FLOP: WEST TO GET FIRST SIGNIFICANT RAIN IN MONTHS

Some areas in the lowlands may see 1 to 2 inches of rain by Monday, with the higher elevations of the Cascades seeing their first snowfall of the season.