Portland, Oregon, is known for its temperate, wet climate, where winter months typically feature persistent, light rain rather than heavy snowfall. The city sits in the Willamette Valley, resulting in mild conditions that generally keep precipitation liquid. While snow is not a regular occurrence, its infrequency makes each accumulation a notable event. Measurable snowfall is a relatively rare annual event in Portland.
Portland’s Average Annual Snowfall
The average yearly snowfall in Portland is low for a major North American city, typically ranging between three and four inches, based on records kept near Portland International Airport (PDX). Many winter seasons pass with little to no measurable snow in the low-lying areas of the downtown core. This official average is a composite of many years where snow is absent and occasional seasons that bring a major winter storm.
The city generally experiences around 18 days per year with some form of snow, though this often includes only a few flakes that do not accumulate. The average temperature of the coldest month, December, often remains above freezing during the day. This limits the potential for snow to form and stick. When snow does fall, the total amount is often less than one inch per storm event, meaning residents experience flurries but rarely a lasting blanket of snow.
When Snow Typically Occurs and Duration
The vast majority of Portland’s snowfall occurs within a short, three-month window, primarily spanning December through February. January is statistically the snowiest month, sometimes contributing one to two inches of the annual total. Climate conditions generally prevent snow from occurring earlier than late November or later than early March.
Once snow falls in the valley, its duration on the ground is typically very short-lived. The maritime influence from the Pacific Ocean keeps temperatures mild, meaning a quick warm-up or the onset of rain often follows a snow event. Accumulations in the metropolitan area rarely last longer than one or two days before melting. Freezing temperatures are not sustained for extended periods, particularly during daylight hours.
Why Snowfall Varies Significantly Across Portland
Snowfall in Portland is highly localized, varying greatly across the metropolitan area due to geographical and meteorological factors. The Columbia River Gorge plays a significant role in creating the necessary conditions for snow in the valley. When high pressure builds over the interior of North America, the Gorge acts as a natural funnel.
This funnel channels cold, dense Arctic air westward into the lower Columbia and Willamette Valleys. This cold air mass, known as the Gorge wind, is necessary for dropping the temperature low enough for snow to fall and accumulate at low elevations. However, the presence of this cold air is often short-lived and dependent on regional weather patterns.
Elevation differences are also a major factor in local snow totals. Higher-elevation areas like the West Hills or Mount Tabor often receive more snow and retain it longer than the downtown core or the airport. This variation means one neighborhood can be snow-covered while another just a few miles away sees only rain.