Story highlights Portland, Oregon, hits record high of 103 for date on Wednesday

Some 15 million are under heat advisories in Pacific Northwest

(CNN) Residents of Portland, Oregon, just want their daily routine -- and temperatures -- to return to normal.

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.