You’ve probably been there: standing in a Santa Rosa parking lot, looking at a sky that’s half-bruised with clouds and half-blazing with sun, wondering why your phone's weather app is basically lying to you.
Living in the North Bay means accepting a certain level of meteorological chaos. If you’re checking the weather santa rosa ca hourly data today, January 17, 2026, you're seeing a high of 64°F and a low of 41°F. But that doesn’t tell the whole story.
Honestly, the "average" temperature in Sonoma County is a myth.
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The Microclimate Reality
Santa Rosa sits in a literal bowl.
To the west, you've got the Sebastopol hills and the "coastal cool" zone. To the east, the Mayacamas Mountains block the valley heat. Because of this, the hourly shift in Santa Rosa can feel like moving between two different states in a single afternoon.
Right now, the current conditions show a quiet night at 56°F with 75% humidity. The wind is a mere whisper at 2 mph coming from the northwest. It’s "cloudy" on paper, but if you’re standing near the downtown SMART station versus up in Fountaingrove, those clouds feel entirely different.
One spot is damp and foggy; the other is just crisp.
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Why the Hourly Forecast is Your Only Hope
Most people glance at the daily high/low and call it a day. Big mistake.
In Santa Rosa, the "Mediterranean" tag means we have massive diurnal swings. Look at today's spread: 64°F down to 41°F. That’s a 23-degree difference. If you leave the house at 8:00 AM in a t-shirt because the "high" looks good, you're going to be miserable by dinner.
Here is what the actual hourly vibe looks like for a mid-January Saturday:
- Morning (6:00 AM – 10:00 AM): It’s biting. We're looking at temperatures hovering near the 41°F low. Humidity is high (around 67-75%), making that 41°F feel even sharper. Patchy fog is common in the interior valleys, according to the National Weather Service.
- Midday (11:00 AM – 3:00 PM): This is the sweet spot. The cloud cover is predicted to hold steady at 10% precipitation chance (basically negligible), and we hit that 64°F peak.
- Evening (5:00 PM onwards): Sunset is early this time of year. As soon as the sun dips behind the coastal range, the temperature drops like a stone. By 9:00 PM, we're back down toward 56°F and sliding.
The "Tule Fog" Factor
If you’re driving Highway 101 tonight or early tomorrow, watch out for the Tule fog.
The NWS Bay Area has already noted that morning fog prevails across the North Bay valleys. This isn't your standard "mist." It's thick, radiator-obscuring stuff that settles in the Santa Rosa plain because the air is trapped.
How to Actually Use This Info
Don’t just look at the temperature. Look at the wind direction. Today, we’ve got a northwest flow at 2 mph, shifting to a northeast breeze at 4 mph later. Northeast winds usually mean drier, slightly warmer air coming over the mountains. It’s why today feels "warm" for January.
Actionable Steps for Today:
- The Three-Layer Rule: A base layer for the 64°F afternoon, a mid-weight sweater for the 56°F evening, and a real jacket for the 41°F late-night drop.
- Fog Watch: If you’re heading toward Sebastopol or Petaluma, expect visibility to tank after 10:00 PM.
- Humidity Management: With 75% humidity tonight, it’s a "wet cold." It’ll seep into your bones more than a dry 40°F would. Plan accordingly if you're hitting the downtown bars or walking the Fourth Street strip.
The sky is cloudy, the air is still, and Santa Rosa is doing that weird mid-winter thing where it pretends to be spring for four hours before reminding you it's actually January.