Seattle, Washington, and Portland, Oregon, were the two major cities with the worst air quality in the world Thursday due to wildfires burning in the Pacific Northwest.
Seattle was ranked No. 1 while Portland was No. 2 on a list of rankings compiled by IQAir, a Swiss air quality technology company. IQAir collects data from individual monitoring stations in cities around the world. Thursday was the second day in a row that Seattle had the top spot.
Beijing was in third place. The Chinese capital has historically been plagued by air pollution, though it met state air quality standards for the first time last year. After Beijing, the city with the fourth worst air pollution was the Canadian city of Vancouver, British Columbia, about 140 miles north of Seattle.
“At this point in the year, it’s unprecedented to see influences from wildfire smoke the way we have been seeing it in the last week or two,” Donna Haga, senior air quality meteorologist with the B.C. Environment Ministry, told the Vancouver Sun.
Much of the smoke near Seattle was coming from Washington’s Bolt Creek Fire, which has burned more than 14,000 acres east of the city, according to NBC News. The Nakia Creek Fire, which forced thousands to evacuate earlier this week, burned near the Washington-Oregon border.
The weather service and the Puget Sound Clean Air Agency had warned people in the Seattle area to limit their time outside and close windows and doors, USA Today reported.
Air quality is expected to improve with rainfall on Friday and Saturday.
“We’re starting to get that October precipitation,” National Weather Service meteorologist Kirby Cook told NBC. “That fall precipitation will be the key to clean the fires out.”
Unusually dry and record-high temperatures in the region have made the fire conditions. On Sunday, Seattle hit 88 degrees, making it the city’s second-warmest October day on record.