The normally temperate city could reach or break its all-time high of 107 degrees (1965 and 1981) by Thursday, the National Weather Service says.
The mercury reached 103 degrees on Wednesday, breaking a 31-year-old record for the day. The city's old record was 96 degrees, which it marked on August 2, 1986.
Some 15 million people in the Pacific Northwest are under excessive heat warnings and advisories. That creates "a dangerous situation in which heat illnesses are possible," the National Weather Service said. Smoke from northwest wildfires hangs over the region, making the situation worse.
The heat is putting a big crimp on life in Portland. Jeff Hough, manager of Front Cooperative Grocery manager, told CNN affiliate KPTV
the store coolers are shutting down and it's difficult to even keep the doors closed.
"The front door, the rubber expanded, so it's not shutting. It got so hot the door won't shut," he said.
Commuting is more difficult. The metro area's public transit system, TriMet, is having service problems because of the heat and computer glitches caused by a system upgrade that went awry, CNN affiliate KATU reported.
TriMet will offer free rides Thursday, but the MAX light rail trains will slow because of excessive heat, and WES commuter train service probably will be suspended Thursday afternoon, with shuttle buses serving WES stations, TriMet said
. "Expect major delays," the transit service said on its website.
Uber and Lyft are offering discounted rides to city cooling centers, KATU reported.
Late Wednesday, Oregon Gov. Kate Brown declared a state of emergency, saying the "hot, dry and windy" conditions are increasing the threat of wildfires. The state also issued an air pollution advisory
because of smoke from wildfires. Medford, in the south of Oregon, was the hottest spot in the state Wednesday with 112 degrees.
Portland wasn't alone: Seattle also broke a daily record. The city reached 90 degrees Wednesday, breaking 89 degrees from August 2, 2009.
CNN meteorologists said Seattle could see 100 degrees this week, which would be only the fourth time in recorded history. Other cities will likely see temperatures hit the triple digits.
Desperate times, desperate measures
The heat has settled in over a region where many homes don't have air conditioning. Only one-third of Seattle residents have it, while Portland's number is about 70%
. Portions of Oregon are a good bit lower
Many Portlanders took to social media to document some of the strange and outrageous ways they are keeping cool, including sticking their feet in a cooler of ice.
One Portland library even started offering free water bottles
to its patrons -- with "no overdue fines!"
It's so hot that Scoop, an ice cream business
, shut down its street cart Wednesday and Thursday for worker safety.
CNN affiliate KIRO in Seattle reported numerous cooling centers were open in the city
Jillian Henze, spokeswoman for the Seattle Hotel Association, said those without air conditioning who are seeking relief will find the supply of rooms scarce. "It is our busiest season of the year; we got cruise ships and summer travel, and rooms are booked up way in advance," she said.
A little relief may be in sight. The high temperatures in Portland should drop to 97 on Friday, 90 on Saturday and 95 on Sunday. the weather service said
. Seattle should see highs of 91 on Friday and 89 on Saturday and Sunday.
What's causing the heat?
A ridge formed in the jet stream, forcing the stronger winds in the upper atmosphere well into Canada, allowing for clear skies in the Pacific Northwest and the temperatures to rise to extreme levels. Friday into the weekend, the jet stream will flatten, allowing for temperatures to ease near normal.
Until then, police and agencies are ensuring those most vulnerable receive help. Portland police on Tuesday tried to get people who usually live on the streets into shelters or cooling centers, CNN affiliate KPTV said
"They really appreciate it because, literally, they are here, they don't want to walk around because it's hot out," Officer Ryan Engweiler told the station. "Just by us driving around giving them the water, giving them the information."