Honestly, if you’re looking at a Sunnyvale CA weather forecast right now, you’re probably seeing a lot of "partly cloudy" icons and feeling a bit bored. But there's a weirdly specific rhythm to South Bay weather that most outsiders—and even some folks living in the 94087—don't quite catch. We aren't just "San Jose light."
Today, January 15, 2026, it is basically a perfect California winter day. We're looking at a high of 67°F and a low of 43°F. Currently, it's about 66°F outside, and with the humidity sitting at 52%, it actually feels a bit warmer—closer to 76°F if you’re standing in the sun near Murphy Avenue.
The Microclimate Reality
Most people assume the Silicon Valley is one giant bubble of 70-degree days. Not really. Sunnyvale sits in this sweet spot where the Santa Cruz Mountains block the worst of the Pacific's damp chill, but we still get a bit of that evening "bay breeze" that'll make you reach for a hoodie the second the sun dips.
Right now, the wind is barely a whisper from the north at 3 mph. It’s calm. But don't let the sunny skies fool you into thinking it's t-shirt weather all night. That drop from 67°F to 43°F happens fast.
What the next few days look like
If you’re planning your weekend, here’s the deal:
Friday stays pretty much the same. High of 66°F, clear skies. It’s Saturday where things get a bit moody. We’re expecting more clouds and a high of 65°F. There’s a tiny 10% chance of rain, which in Sunnyvale usually just means "your car gets spotted but you won't need an umbrella."
By Tuesday, we might see the mercury dip a little further to 63°F. Still, compared to the rest of the country dealing with "Arctic revenge" (as some news outlets are calling the current eastern cold snap), we’re living in a different world.
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Why January in Sunnyvale is Sneaky
January is technically our "cloudiest" month. Statistically, the sky is overcast or mostly cloudy about 54% of the time. But "cloudy" here isn't the gloomy, soul-crushing gray of London or Seattle. It's more of a high-altitude haze that breaks by 11:00 AM.
The real thing to watch for is the fog. This morning had some dense patches. When the humidity hits 65% like it did earlier today, and the north wind stays light, the valley floor turns into a soup bowl. It makes the commute on the 101 a nightmare, but it usually burns off before lunch.
The "Dry" Winter
We’re currently in a bit of a dry spell. For the next ten days, the precipitation chance stays at 10% or lower. While that's great for hiking at Rancho San Antonio, it's actually a bit weird for mid-January. Usually, we expect about 3.22 inches of rain throughout the month. This year, the Pacific Southwest is leaning a bit warmer and drier than the historical average.
Experts from The Old Farmer's Almanac actually predicted a warmer winter for us back in late 2025, and so far, they aren't wrong. We are trending about 2 degrees above the typical January average.
Survival Tips for the South Bay Winter
If you're new here, or just visiting one of the tech campuses, the Sunnyvale CA weather forecast is only half the story. The other half is the "Bay Area Layering" law.
- The 2:00 PM Switch: At 2:00 PM, you will be sweating in a sweater. At 5:15 PM (sunset is at 5:14 PM today), you will be shivering in a t-shirt.
- UV is Low but Real: The UV index is only a 2 today, but because the air is so clear, you can still get a bit of a "windburn" look if you're out all day.
- Humidity Matters: At 52% humidity, the air doesn't hold heat well once the sun goes down. That 43°F tonight is going to feel crisp.
Looking Ahead to Next Week
Expect the sun to keep its streak going. Monday and Tuesday look like carbon copies of today, with highs in the mid-60s. We might see a slight cooldown toward Wednesday, January 21, as highs drop to 60°F.
Wait for the "first frost" window, which usually hits between January 21 and January 31. We haven't seen a real hard freeze yet this year, and looking at the current Sunnyvale CA weather forecast, we might dodge it entirely this season.
Next Steps for Your Week:
Keep your light jacket handy for the evenings, but go ahead and plan those outdoor lunch meetings through Friday. If you have outdoor plants that are sensitive to the mid-40s, you might want to move them closer to the house by Sunday just in case that 46°F low feels a bit sharper with the northeast wind.