Winter in Sonoma County is weird. One minute you're looking at a 10 day weather forecast Santa Rosa update that promises nothing but "partly cloudy" skies, and the next, you’re watching a localized atmospheric river dump two inches of rain on your heritage oaks.
Honestly, if you've lived here long enough, you know the "official" numbers only tell half the story.
Right now, as of Sunday, January 18, 2026, we’re sitting in a pocket of classic Northern California winter. The air is crisp—maybe a bit more than "crisp" if you're out at dawn—but the sun is doing its best to keep things civil. According to the latest data from Google Weather, the current temperature is sitting at a chilly 38°F.
It’s the kind of morning where you regret not warming up the car.
The Immediate Outlook: Sun vs. Shivers
Today isn't going to be a total wash. In fact, we’re looking at a high of 66°F under partly sunny skies. That’s a massive swing from the morning low. If you’re heading out to Trione-Annadel State Park or just grabbing a coffee downtown, the "onion method" of dressing isn't just a suggestion; it’s a survival strategy.
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The wind is barely a factor today, coming in from the south at a lazy 3 mph. Humidity is high—73% for the daily average—which means that 66 degrees might feel a little "heavy" compared to a dry summer heat.
Here is the thing: the 10-day trend looks suspiciously stable, but don't let that fool you.
Deciphering the 10 Day Weather Forecast Santa Rosa
When you look at the extended projections, we see a pattern of highs in the mid-60s and lows dipping into the high 30s or low 40s. Monday and Tuesday (January 19-20) are expected to stay bright, with highs hovering right around 66°F.
It's essentially "fake spring."
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- Sunday, Jan 18: High 66°F | Low 37°F (Partly Sunny)
- Monday, Jan 19: High 66°F | Low 46°F (Sunny)
- Tuesday, Jan 20: High 66°F | Low 47°F (Partly Cloudy)
But notice that shift toward the middle of next week. By Wednesday and Thursday, the clouds start to thicken. We’re looking at highs dropping slightly to 64°F and 62°F.
Basically, the "Mediterranean" part of our climate is taking a breather.
By the time we hit next Saturday, January 24, there’s a genuine chance of rain on the horizon. It’s not a deluge yet—most models are showing it as a "chance" rather than a certainty—but the temperature will likely flatline around 60°F.
Why the "Average" Forecast is Often Trash
If you search for Santa Rosa weather, you'll see historical averages of 58°F for January. We’re currently beating that by nearly 10 degrees. This happens because Santa Rosa is tucked into a valley that traps heat during the day but lets it bleed out the moment the sun goes behind the coastal range.
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Wanderlog and WeatherSpark both note that January is technically our most humid month. That humidity (averaging 78% historically) is what makes the 40-degree nights feel bone-chilling. It's a "wet cold."
Also, microclimates are real. If you’re in Bennett Valley, you might be five degrees cooler than someone sitting in a backyard in Rincon Valley. The 10-day forecast is a "best guess" for the city center, but your porch thermometer will almost certainly disagree.
What This Means for Your Week
You’ve got a solid window of dry weather for the next 5 to 6 days. If you’ve been putting off gutter cleaning or outdoor projects, do them now.
The UV index is low (around 2), so you won't fry, but the air quality is generally good this time of year unless we get a stagnant high-pressure system that traps fireplace smoke in the valley floor.
Practical Next Steps:
- Layer up: Plan for a 30-degree temperature swing between 7:00 AM and 2:00 PM.
- Check the Saturday rain: If you have outdoor plans for Jan 24, have a Plan B. The "chance of rain" is currently hovering around 30-40% depending on which model you trust, but in Sonoma County, that often turns into a soaking afternoon.
- Irrigation: With highs in the mid-60s and low rain, don't let your sensitive potted plants go completely bone-dry, even if it is "winter."
The 10-day stretch is looking mostly benign, but keep an eye on that transition toward the end of the month. Northern California winters love to start quiet and end with a splash.