A string of warm days in the Portland area is on the verge of breaking a 30-year-old record.
The last time the region had four consecutive days with temperatures above 70 degrees in March was in 1994. That record will break Tuesday if temperatures pass that threshold. The National Weather Service projects temperatures will reach 71 degrees.
“On average, we see one day in March at about 70,” Clinton Rockey, a meteorologist with the agency, said. “So it’s quite a treat to have this many days at about 70 this early in the season.”
Despite the warm spell, Oregonians west of the Cascades should keep their rain jackets and sweaters handy as cooler weather moves in from the coast.
By Wednesday, daytime temperatures in the Portland region are expected to only hit the high 50s and stay that way for the rest of the week, accompanied by lots of rain.
Gardeners should also hold off on planting anything that isn’t hardy enough to withstand overnight freezing temperatures. There’s a good chance that the year’s final freeze has yet to come.
“Our last 32 typically is the last week of March across most of the [Portland] metro,” Rockey said. “Once you get in the outlying areas of the metro, especially the west and the south of town, you have to wait into early April to mid-April for your last frost to come through.”
Heavy snowstorms in January and February helped bring snowpack levels up to normal across the western Cascades. The Willamette Basin is up to 108% of median historic snowpack levels. Still, much of that could dry up by May, depending on how the spring plays out.
The warmer-than-usual winter temperatures were partly due to it being an El Niño year, in addition to global warming from climate change. El Niño is a phenomenon in which sea-surface temperatures across the east-central equatorial Pacific become warmer than usual. It happens every 3-5 years.
Forecasters expect those warmer El Niño temperatures to transition into cooler La Niña temperatures this fall. The cool-off could also mean fewer extreme hot days this summer, but Rockey said that’s difficult to predict with certainty.
As far as what next winter could bring, Rockey said La Niña usually means more rain and cold temperatures, but that’s also a tossup.
“How cold? Too early to tell. How much above-normal rain? That’s also too early to tell,” Rockey said. “Because no El Niño and no La Niña are ever the same.”
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