MENDOCINO CO., 9/3/26 — The National Weather Service has posted a frost advisory for the northern interior of Mendocino County from 3 to 9 a.m. Friday, Sept. 4, with lows forecast between 34 and 38 degrees.
The advisory covers the Willits, Laytonville, Leggett and Potter Valley areas and Round Valley. It doesn’t include Ukiah Valley or Anderson Valley, where Friday morning lows are forecast in the mid-to-upper 40s.
The weather service’s Eureka office issued the advisory at 12:39 p.m. Thursday, Sept. 3. Its afternoon forecast discussion says forecasters made the call despite some doubt about how much the sky will clear overnight, because lows in the mid-30s are landing “so early in meteorological fall.” Meteorological fall began Sept. 1.
A cold, unstable low-pressure system is passing over the region Thursday, with a chance of showers into the evening. If the clouds clear behind it and fog doesn’t form, the forecast office says areas of frost are likely across the interior. Clouds or fog that hang on overnight would blunt the cold.
Forecast lows for Friday morning: 38 in Covelo, 39 in Potter Valley, 41 in Laytonville and 43 in Willits.
The weather service says sensitive outdoor plants may be killed if left uncovered and advises protecting tender plants now. Late tomatoes, peppers, cukes, and some outdoor crops weeks from harvest are the plants at risk.
The forecast discussion calls for chilly interior nights and frost chances through the weekend, with a possible short warmup early next week and more chances of showers and isolated thunderstorms after that.