From midnight Friday until 9 a.m. Saturday, Oct. 31, the National Weather Service in Portland has a frost advisory out for the Portland metro area and a freeze watch for the Tualatin Valley and the central Willamette Valley. The office’s Thursday alert warned that frost could harm sensitive outdoor plants and that tender plants may die if they are left uncovered. It will also be the last frost or freeze alert the office issues this year.
Which counties and valleys are covered
The frost advisory, issued at 11:14 a.m. Thursday, covers a wide sweep of northwest and west-central Oregon and southwest Washington. That includes the Oregon coast, the Central Oregon Coast Range, the Lower Columbia River, the Portland metro area, the Columbia River Gorge above 500 feet, the Cascade foothills of Marion, Linn and Lane counties, the Willapa Hills, and the Cowlitz and Clark county lowlands. The office set the threshold plainly: temperatures of 36 degrees or lower will produce frost.
The freeze watch, for the same overnight window, is aimed at the places most likely to dip to 32 degrees or below. It covers the Clackamas County Cascade foothills, the East and West Central Willamette Valley, the Tualatin Valley and the Central Oregon Coast Range lowlands in Oregon, plus the North Clark County lowlands in Washington. A republished copy of the watch lists the same zones and says a freeze could kill crops and other sensitive vegetation and could damage unprotected outdoor plumbing.
Forecasters were confident in the setup. The office’s late Thursday forecast discussion, issued at 10:58 p.m., said clear skies and nearly calm winds should let temperatures fall sharply by Saturday morning. It put the chance of frost at 50 to 90 percent across most of the forecast area, and the chance of below-freezing temperatures at 50 to 85 percent in most inland valleys outside the Portland metro. The discussion said similar cold mornings are likely Sunday and Monday, though cloud cover makes Sunday less certain.
The last frost alert of 2026
The Portland office issues frost and freeze headlines only during the growing season, from April 1 through Oct. 31. In its discussion, the office said no more frost or freeze headlines will be issued after Saturday, even if the same cold returns next week…