Driving the length of California on Interstate 5 is basically a rite of passage, but honestly, treating it like a standard highway run is where most people mess up. You’ve got nearly 800 miles of asphalt stretching from the Mexican border all the way to Oregon, and the weather on i5 California is never just "one thing."
Right now, as of January 18, 2026, the state is sitting in a bit of a post-storm lull, but don't let the clear skies in the Central Valley fool you. While the current temperature in the general California corridor is a mild 52°F with a light 3 mph northwest wind, the microclimates along this route are notoriously fickle. Just a couple of weeks ago, a massive atmospheric river slammed the state, and we're still seeing the fallout in terms of road repairs and saturated hillsides.
The Grapevine and Tejon Pass: The "Big Bad" of SoCal
If you’re heading north out of Los Angeles, you’re hitting the Grapevine. Most people think "Southern California" means sunshine, but the Tejon Pass (elevation 4,144 feet) is a different beast entirely. Today, it's actually fairly decent—around 59°F for the high with 33% humidity—but that can flip in an hour.
Earlier this month, we saw high wind advisories from the Los Angeles/Kern County line up to the Grapevine. When those winds start gusting over 45 mph, Caltrans starts pulling over high-profile vehicles like campers and trailers. It's not just about the wind; it's the "slip-outs." Recent rains have turned the clay layers in these mountains into literal grease. Caltrans is currently working on guardrail upgrades and repaving from Lake Hughes Road to Vista Del Lago Road, so expect lane closures through at least January 17th and 18th.
💡 You might also like: Airports Near Amalfi Coast: What Most People Get Wrong
The real danger here is the "Tule Fog" in the valleys just north of the pass. It’s thick, it’s grey, and it’s the reason for those massive multi-car pileups you see on the news. Today's humidity is at 84% in some areas, which is the perfect recipe for that pea-soup visibility.
The Central Valley: Boring but Deceptive
Once you drop down into the San Joaquin Valley, the drive feels flat and predictable. It’s not. Between Tracy and Stockton, a dense fog advisory is a common winter guest. Basically, the air gets trapped, the "No Burn" day alerts go out (like they did this morning due to poor air mixing), and visibility drops to zero.
The forecast for the next few days in this region looks like this:
- Monday, Jan 19: Sunny with a high of 63°F. Perfect for the MLK holiday drive.
- Tuesday, Jan 20: Cloudier, hitting 65°F.
- Wednesday, Jan 21: Mostly cloudy, sticking around 63°F.
While it stays dry, the temperature swings are wild. You'll see a low of 41°F on Tuesday night. If you're hauling goods or just road-tripping, that's a 20-degree drop that can catch your tire pressure off guard.
📖 Related: Getting the Distance From Williamsburg VA to Virginia Beach Right: Why It Isn't Just One Number
Northern Exposure: The Siskiyou Summit
This is the part of the weather on i5 California that actually scares seasoned truckers. As you move past Redding and up toward Mount Shasta and the Siskiyou Summit, you're entering the danger zone.
Even on a "clear" day like today, the pavement temperature at the summit is hovering near freezing. We’re talking 38°F with 4 inches of roadside snow still sitting there from the last system. The California Department of Transportation (Caltrans) and ODOT are currently requiring drivers to carry chains over the mountain passes.
👉 See also: Why Fun Things to Do in Alpharetta Keep Getting Better Every Year
"The first snow of the season typically catches drivers unprepared," says Jeremiah Griffin, a regional manager at ODOT.
He’s right. Even if the sun is out, black ice hides in the shadows of the tree-lined stretches near the Oregon border. If you’re driving through Hornbrook or Montague in the early morning hours, expect icy patches.
Actionable Tips for the I-5 Corridor
Don't just wing it. If you're hitting the road this week, here is what you actually need to do:
- Check the QuickMap: Caltrans has a "QuickMap" app. Use it. It shows real-time lane closures, like the ones currently hitting I-5 in Burbank for repaving (Jan 23-26) and the ongoing work near Castaic.
- The Gas Tank Rule: Never let your tank drop below half once you pass Redding or before you start the climb into the Grapevine. If the road closes due to snow or a wreck, you’ll need that fuel to keep the heater running for hours.
- Chain Mastery: Don't be the person learning how to put on chains in a slushy turnout at 2:00 AM. Practice in your driveway.
- Fog Etiquette: In the Central Valley, if you hit a fog bank, do not turn on your high beams. It just reflects back at you. Use fog lights or low beams and follow the white line on the right, not the taillights in front of you.
The weather on i5 California is manageable, but only if you respect the geography. From the 85°F peaks in some southern pockets earlier this month to the freezing winds of the north, it’s a marathon, not a sprint. Pack a blanket, grab an extra gallon of water, and keep your eyes on the horizon.