It’s official: Sunday was the hottest day ever recorded in Seattle.

The scorching milestone was set at 5:29 p.m., when the temperature hit 104 degrees, the highest on record, dating back to at least 1945, according to the National Weather Service.

The temperature had tied the previous record of 103 (set in 2009) earlier Sunday afternoon, as an atmospheric “heat dome” baked the Pacific Northwest with an unprecedented stretch of triple-digit thermometer readings. It never got cooler than 73 degrees — a record-high minimum temperature.

By 7 p.m. the temperature readings had cooled to a mere 99 degrees, said National Weather Service meteorologist Jeff Michalski. “I can’t believe I am saying that,” he added.

Sunday’s record could be short-lived, as Monday’s forecast is calling for temperatures that could reach 110 degrees.

Some relief should arrive by Wednesday, when temperatures are expected to drop into the 80s in the Seattle metropolitan area. “By then the oppressive heat is pretty much over,” Michalski said.

The heat records smashed this week date back to at least 1945, since official weather service readings have been taken at Seattle-Tacoma International Airport. Michalski said Sunday’s high temperature also beats anything recorded at Seattle’s old federal building, where they’d been taken previously, dating back to the 1890s.