Portland is starting Monday, October 5, with fog and mist before a sunny, unseasonably warm stretch takes over. Temperatures near 55 degrees early are expected to climb to about 76 this afternoon, with no rain in the forecast.
Fog Gives Way To A Warm Afternoon
Morning fog may slow visibility in parts of the Portland metro area and nearby valleys, especially during the commute. The National Weather Service in Portland said some locations could briefly see visibility drop below a half-mile, while daytime heating and light north-northwest winds should clear the low clouds.
Monday night will be partly cloudy with a low near 55 degrees. Tuesday stays mostly sunny with a high around 75, followed by a warmer Wednesday near 78 and a sunny Thursday that could reach 81.
An Oregon Benchmark for October Warmth
Salem offers a reference point, but not a Portland record: according to the National Weather Service Portland’s Salem 2022 Annual Climate Report, Salem’s 92-degree high on October 15 set a daily record, and the month ranked as the city’s third-warmest October on record since 1892. Salem also recorded nine October days with highs of 80 degrees or higher.
How This Forecast Fits Longer-Term Climate Context
The Salem report does not give Portland International Airport’s October record temperatures or climate normals, so its figures cannot show how an 81-degree forecast compares with those Portland benchmarks. Research has documented significant autumn warming in Portland and the Willamette Valley. For longer-term context, Oregon State University’s Institute for Natural Resources projects that July through September in the Willamette Basin will warm about 2°C (3.6°F) more than winter. That is a projection for summer months, not a record of observed October or autumn temperature changes.
Cooler Weather Arrives Friday
The warm spell begins to fade Friday, when Portland is expected to see a mostly sunny high near 73 and a small chance of rain. The odds remain low, with the forecast calling for no more than a slight chance of light precipitation inland.
Temperatures drop further over the weekend, with highs near 66 Saturday and 67 Sunday. Saturday night could fall to around 48 degrees, while Sunday night stays mostly clear with a low near 48.
Coastal Fog And Boating Advisories
The National Weather Service is also warning of dense fog over coastal waters and the Columbia River Bar through Monday afternoon, along with a Small Craft Advisory for portions of the Oregon coast. Those conditions are separate from Portland’s inland forecast, which remains dry and increasingly sunny through Thursday.
