Honestly, living in the San Gabriel Valley means you're used to a certain kind of predictability. But if you’ve been looking at the San Dimas weather 10 day forecast lately, things are looking a bit more "California winter" than usual. We aren't talking about a frozen tundra, obviously, but there’s a specific shift coming that might catch you off guard if you're planning a hike at Bonelli or a trip to the Raging Waters area (even if it's just for a walk).
Right now, as of Saturday, January 17, 2026, it’s a bit of a mixed bag. We’re sitting at a comfortable 60°F with a lot of cloud cover. It feels like the air is holding its breath.
The Immediate Breakdown
The next few days are actually kind of great. Saturday and Sunday are holding steady with highs of 75°F. That’s that classic "is it actually winter?" vibe we get here.
Monday, January 19, is looking like the pick of the week. It’ll be sunny with a high of 72°F. If you have the day off for MLK Day, it’s basically perfect for being outside. No rain, just clear skies.
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But here is where the San Dimas weather 10 day forecast starts to pivot.
By Tuesday, we drop to 71°F, and by Wednesday, the clouds really start to move in. We’re looking at 69°F mid-week, and the humidity is hovering around 33%. It's not "wet" yet, but you can feel the atmosphere shifting. The nights are staying pretty crisp, too, bottoming out around 50°F. You’ll definitely want that heavier sweater if you're out late.
When the Rain Actually Hits
People always ask if it’s actually going to rain or just "mist" like it usually does.
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Looking at next weekend—specifically Saturday, January 24—the probability of rain jumps up significantly. We’re looking at a 35% chance during the day and a 45% chance of showers that night. Sunday, January 25, keeps that energy with a 45% chance of rain and a high of only 67°F.
- Saturday Night: Showers likely, low of 49°F.
- Sunday Morning: Continued rain, humidity spiking to 54%.
- Monday Recovery: Mostly cloudy, but the rain should taper off back to 10% chance.
It’s not a deluge, but it’s enough to make the trails at San Dimas Canyon a muddy mess. If you're planning on mountain biking or hitting the dog park, maybe aim for that Monday-Tuesday window instead of the following weekend.
Humidity and Wind Factors
One thing people overlook in the San Dimas weather 10 day forecast is the wind. We’re seeing very light breezes right now—about 3 to 5 mph coming mostly from the north and northwest. This isn't Santa Ana territory. It’s more of a stagnant, cool air mass.
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The UV index is also staying incredibly low, peaking at a 3 on Monday and hovering around 1 or 2 for most of the week. Basically, you won't be getting a tan, but the air quality usually stays a bit better when we have this kind of cloud movement.
Why This Matters for Your Week
San Dimas is in a unique spot because we get that canyon influence. While it might be 75°F in the sun on Sunday, the moment the sun dips behind the hills, that 52°F low is going to feel a lot colder because of the dampness in the air.
If you’re heading to the local high school games or just grabbing dinner downtown, the layering rule is in full effect. The "January 21st" clear sky window is usually the brightest part of the month historically, and this year seems to be following that trend before the weekend system moves in.
Keep an eye on that Friday/Saturday transition. That’s the most volatile part of the current 10-day outlook.
Practical Steps for the Week Ahead
- Garden Check: With the rain coming next weekend, hold off on any heavy watering by Thursday. Let nature do the work on Saturday and Sunday.
- Trail Safety: If you're hitting the foothills, do it before Friday. Once that 45% rain chance hits on Sunday, the decomposition granite on the trails becomes slick and unpredictable.
- Home Prep: Check your gutters now while it's 75°F and sunny on Sunday. Don't be the person cleaning them out in 49°F rain next Saturday night.
- Dress Code: Light jackets for the 70°F days, but keep a real coat in the car for any post-sunset plans, as the drop-off is sharp.