VANCOUVER, Wash. – The year was 1930, and it was freezing – literally.
The Portland area was coming off a 19-day stretch of subfreezing temperatures. From Jan. 8 to Jan. 26, the daily high temperature never cleared 32 degrees. It was the longest, most consistent cold spell in the region’s recorded history, according to data from the National Weather Service.
The Columbia River was solid enough to land a plane. That’s a fact, not an expression. On Jan. 31, the moment was immortalized on film – a photograph of Clarence and Glenn Murray standing next to their biplane on the still-frozen river, propeller blurred in motion after the aircraft had glided under the Interstate 5 Bridge.
The river actually froze solid a handful of times in the early 20th century.
But it hasn’t frozen since the 1930 cold spell and likely won’t freeze again. There are two primary reasons for that: Dams increase the pace of the waterway and a warming climate.
Construction on Bonneville Dam started in 1933, three years after the big Columbia chill.
It’s no coincidence that its construction marked the end of the river’s period of freezing. As one of 11 dams on the Columbia River, the Bonneville helps keep the water flowing fast enough to prevent ice from forming.
Faster-moving water means it would have to get even colder to freeze the Columbia River. With sustained freezing temperatures rarer than they were a century ago, the likelihood of that is slim to none.
“You’d need prolonged, subfreezing temperatures to counteract the temperature difference from the groundwater flows in the river for the water to freeze at the air surface,” said Kevin Wingert, public affairs specialist at Bonneville Power Administration, in an email.
Long periods of subfreezing temperatures aren’t as common anymore.
Winters are more mild than they used to be. In January 1875, for instance, the average minimum temperature in Portland was 24.6 degrees. A century later, the average minimum temperature in January 1975 was 36.1 degrees.
Last January, the average low was 40.8 degrees.
The warming trend will likely continue. The National Climate Assessment estimates an increase in average annual temperature of 3.3 degrees to 9.7 degrees in the Northwest by 2070 to 2099.
So if you’re hoping to stroll to Portland for a night out – like four couples supposedly did in 1917 when they walked across the solid river for a night out dancing – you might be out of luck, or you could always take the bridge.
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