Honestly, if you stepped outside in Riverside this morning, you probably noticed it: that weirdly perfect "winter" air that feels more like late April. It is Sunday, January 18, 2026, and while the rest of the country is shivering through the usual January slog, we are looking at a thermometer that says 72°F right now.
Kinda crazy, right?
But that is just the beginning of the story for the week ahead. If you’ve got plans to head out to Fairmount Park or grab some outdoor seating at the Food Lab, you’re basically in luck. The 5 day weather forecast riverside ca is showing a stretch of warmth that actually beats out our historical averages by a good ten degrees.
The Breakdown: What the Next 5 Days Really Look Like
Let’s get into the specifics because the vibe shifts a bit as we move toward the weekend.
Sunday, January 18 (Today)
We are topping out at 79°F. It’s mostly cloudy at the moment with 19% humidity, which is pretty dry even for us. There was a tiny 10% blip for rain earlier, but it’s looking more like a "partly sunny" kind of afternoon. Tonight, it drops to a crisp 44°F. That’s a 35-degree swing. Classic high desert influence.
Monday, January 19 (Tomorrow)
If you’re off for the holiday, the weather is cooperating. We hit 79°F again. Full sun. No clouds to hide behind. The wind is shifting to come from the northeast at 5 mph, which usually signals those Santa Ana pressures building up behind the mountains, though they aren't hitting full force yet.
Tuesday, January 20
The heat peaks early in the week. Expect 78°F and mostly sunny skies. It’s the kind of day where you’ll want a light jacket for the 47°F morning, but you’ll be regretting it by noon.
Wednesday, January 21
Things start to "cool" down, if you can call 75°F cool. The clouds are coming back in, making it mostly cloudy throughout the day. Humidity ticks up slightly to 26%, and we have a 10% chance of a stray sprinkle. Nothing to cancel plans over, but keep an eye on the windshield.
Thursday, January 22
We finally see some more traditional winter numbers with a high of 73°F. Still way above the usual January average of 65°F, but the western wind is picking back up. Nighttime brings a 15% chance of rain, so we might actually see some wet pavement by Friday morning.
Why is it so Warm?
Normally, Riverside in January is a bit more temperamental. Historical data from sources like the National Weather Service and the Old Farmer's Almanac usually put us in the mid-60s this time of year. So why the 80-degree flirtation?
It basically comes down to high-pressure ridges sitting over the Southwest. When that high pressure parks itself over the Great Basin, it pushes air down toward the coast. As that air drops in elevation toward the Inland Empire, it compresses and heats up. That’s why Monday and Tuesday feel like a summer teaser.
Survival Tips for the Temperature Swings
Living here means mastering the art of the "Riverside Layer." You can’t just wear a sweater and call it a day.
- The Morning Strategy: Since we are hitting lows of 44°F and 45°F, you need a heavy outer layer before 8:00 AM.
- The Midday Pivot: By 2:00 PM, that sweater is going to feel like a sauna. Wear a breathable base layer.
- Hydration: With humidity hovering between 19% and 33%, you're losing moisture faster than you realize.
- Sunscreen: Even with a UV index of 2 or 3, that direct January sun at 79°F can still catch you off guard if you're out hiking Mt. Rubidoux.
What to Do Next
If you’re planning a garden or just trying to keep your lawn alive, keep the water running a little longer this week. The lack of significant rain (only 5-10% chances) combined with these temperatures means the soil is drying out faster than a typical January.
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Check your irrigation timers today—make sure they haven't been dialed back too far for a "winter" that hasn't actually shown up yet. If you're heading out, Monday is the pick of the week for outdoor activities before the clouds settle in on Wednesday.