You’ve lived in the East Bay long enough to know the drill. One minute you’re looking at the hills thinking it’s a perfect day for a Lake Chabot hike, and the next, a wall of gray rolls over from the canyon and ruins your car wash. Honestly, checking the 10 day forecast castro valley residents rely on is basically a local pastime.
Right now, we are sitting in that weird mid-January pocket where the weather can’t quite decide if it wants to be "crisp winter" or "pre-spring." If you’re looking at the window today, Sunday, January 18, 2026, it’s actually looking pretty decent. We’ve got a high of 64°F and a low of 47°F with some partly sunny skies. It’s the kind of day where you definitely need a light jacket for the shade but might actually break a sweat if you’re walking up those steep residential hills.
The Short Term Breakdown: Sun vs. Clouds
Tomorrow, Monday, January 19, looks like a carbon copy of today in terms of the high temperature, holding steady at 64°F. The big difference? It’s going to be full-on sunny. If you have the day off for the holiday, this is your window. Grab it. The low dips a bit further to 44°F, so don’t let that afternoon sun fool you into leaving your heater off at night.
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Things start to shift Tuesday. The thermometer takes a noticeable dive. We’re looking at:
- Tuesday, Jan 20: High of 59°F, fully cloudy.
- Wednesday, Jan 21: High of 59°F, still cloudy.
- Thursday, Jan 22: High of 57°F, cloud cover persists.
Basically, from Tuesday through Thursday, the sun is going on a bit of a hiatus. It’s not necessarily "stormy," but it’s going to feel damp and gray. Humidity is expected to spike into the 70% to 80% range during these days, which in Castro Valley usually means that "bone-chilling" cold that feels way colder than the actual number on the screen.
Will It Actually Rain?
This is the part everyone cares about. According to the current 10 day forecast castro valley data, we aren't seeing any "atmospheric river" level events, which is a relief given how soggy the Bay Area can get in January.
The chance of precipitation stays remarkably low—mostly around 10% for the next several days. Even on Saturday, January 24, when the chance "spikes" to 20%, it’s more likely to be a light drizzle or just heavy mist rather than a downpour. If you’re planning an outdoor event for next weekend, Saturday is the "riskiest" day, but even then, the high is only 56°F. It’s going to be chilly, so maybe move the party to the garage or keep the fire pit roaring.
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Looking Toward Late Next Week
The clouds finally start to break up as we head toward the end of the month. Friday, January 23, brings back the "partly sunny" vibes with a high of 58°F.
By the time we hit Monday, January 26, and Tuesday, January 27, we’re back to mostly sunny and sunny conditions. Temperatures will hover right around 58°F to 59°F. It’s classic Northern California winter—cool, clear, and perfectly fine for a morning run as long as you have the right layers.
What Most People Get Wrong About Local Forecasts
Kinda funny how we think the weather in Hayward or San Leandro is exactly the same as ours. It isn't. Because Castro Valley is tucked into those rolling hills, we often get trapped air. This leads to that morning valley fog that lingers way longer than it does down by the water.
If the forecast says "sunny," but you wake up and can’t see the end of your driveway, don't panic. Usually, that stuff burns off by 11:00 AM once the sun gets high enough over the ridge.
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Actionable Steps for the Week Ahead
- Layer Up Early: Since we're seeing nearly 20-degree swings between the daily high and low, the "t-shirt under a hoodie" combo is your best friend this week.
- Check the Humidity: With humidity hitting 82% on Thursday and Friday, your house might feel extra clammy. If you’ve got a dehumidifier, those are the days to run it.
- Plan Your Outdoor Work: Monday is the last "warm" day (64°F) for a while. If you need to do yard work or paint something outside, do it tomorrow before the mercury drops into the 50s for the rest of the week.
- Saturday Caution: Keep an eye on that 20% rain chance for Saturday. It's low, but it's the highest of the week.
Stay warm out there, and don't let the mid-week gray get you down—the sun is slated for a comeback by next Monday!