When to expect Portland's first freeze
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Oregonians should prepare for a cooler and slightly wetter winter thanks to La Niña's anticipated arrival, per the latest National Oceanic and Atmospheric Administration outlook.
Why it matters: We're about a month out until Portland could see its first freeze, too — when temperatures reach 32° or below.
Driving the news: Last month was Portland's second-hottest September on record, and while that warm, sunny weather has continued into October, above-average precipitation and snowfall combined with cold temperatures are not far away.
What they're saying: An expected "weak" La Niña winter — when ocean temperatures are cooler than normal — is potentially very good news for Oregon's snowpack, state climatologist Larry O'Neill told Axios in an email, "since cooler temperatures are more likely to preserve whatever precipitation falls as snow in the mountains."
- "So a good snow and ski season is favored!" O'Neill said, adding that he doesn't believe the start of the season will be delayed, as it was last year.
Zoom in: Between 1991 and 2020, the average first freeze date in Portland was Nov. 14, according to the nonprofit climate research group Climate Central.
Between the lines: First freeze is slightly different from "first frost," which is related not just to temperature, but to the amount of moisture in the air.
- The average first freeze date has shifted in many parts of the country in 1991–2020 compared to 1981–2010 amid climate change.
Flashback: At the Portland airport, the earliest freeze on record happened on this day (Oct. 8) in 1985, while the latest happened on Dec. 29, 2012, according to National Weather Service historical data.
- Every year since 1938 has had at least one day below freezing at the airport, O'Neill said. So don't expect this one to be any different.
The bottom line: Get those jackets out of storage and sweep those chimneys.