Rigby weather is weird. Honestly, if you’ve spent any time in Jefferson County, you know that the standard 10-day outlook is basically just a polite suggestion from a computer in another state. Today, Sunday, January 18, 2026, we’re looking at a high near 38°F, which feels downright tropical compared to the sub-zero snaps we usually get this deep into January.
But here is the thing about a weather forecast Rigby Idaho locals actually trust: it’s never just about the temperature. It’s about the "Rigby Wind" and those morning inversions that turn the valley into a freezer chest.
The Immediate Outlook for Rigby
Right now, the sky is showing abundant sunshine. That sounds great for a Sunday drive, but don’t let the blue sky trick you into leaving your coat in the truck. Even with a high of 37°F or 38°F, those light and variable winds can still bite if you're standing in the shade.
Tonight is going to drop fast. We're looking at a low around 13°F. If you’re heading out toward Ririe or over to Idaho Falls, watch for patchy freezing fog. This is a classic Rigby move. The air stays clear all day, then as soon as the sun dips behind the Big Holes, the humidity spikes and the visibility drops to less than a mile in some spots.
Looking at the week ahead, Monday stays mostly sunny with a high of 35°F. By Wednesday and Thursday, things get a bit moodier. Cloud cover will increase to about 60%, and while we aren't seeing a massive "dump" of snow in the immediate cards, there’s a 15% to 44% chance of "a few flakes" by Friday.
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Why Rigby Weather is Different from Idaho Falls
You’d think being only 15 miles apart would mean the weather is identical. It’s not. Rigby sits at an elevation of about 4,862 feet. It’s just high enough and just positioned enough in the "rain shadow" of the central mountains that we get a very specific dry-cold mix.
- The Inversion Effect: Cold air likes to settle in the valley. While the mountains might be sunny and 40 degrees, Rigby can get stuck under a gray lid of clouds and freezing temperatures for days.
- The Wind Factor: March is technically our windiest month, but January averages around 12.7 mph. That doesn't sound like much until you’re trying to move a frozen gate at 6:00 AM.
- Snow Reality: We average about 6 inches of snowfall in January. It’s not the heaviest month—that’s usually December—but the snow we do get tends to stay because it rarely gets warm enough to melt completely.
The 10-Day Breakdown (Estimated)
If you’re planning your week, here is the rough trajectory based on current models for late January 2026.
Early Week (Jan 19-21): Highs in the mid-30s, lows in the teens. Boring, dry, and cold. Perfect for getting chores done before the next system moves in.
Mid-Week (Jan 22-23): We start seeing more overcast skies. Expect highs to hover around 37°F. There’s a persistent signal for light precipitation—likely just a dusting, but enough to make the Highway 20 overpasses slick.
Next Weekend (Jan 24-25): Temperatures might actually dip a bit closer to the freezing mark for the high, staying around 30°F to 32°F.
What to Actually Wear
People from California come here and think a "heavy jacket" is enough. It's not. If you are out in Rigby during a January inversion, you need layers that stop the wind. The humidity here hits near 100% on some winter mornings, which makes the "dry cold" feel surprisingly damp and bone-chilling.
Basically, you’ve got to have:
- A base layer that wicks moisture (not cotton!).
- A middle insulating layer (down or heavy fleece).
- A wind-breaking shell.
- Gloves that actually have some dexterity, because fumbling with frozen locks is the worst part of a Rigby winter.
Common Misconceptions About the Area
A lot of people check the "Idaho Falls" forecast and assume it's the same. Because of the way the Snake River flows and the specific orientation of the valley, Rigby can often be 3-5 degrees colder at night than the city. We also tend to get a bit more of that "lake effect" moisture from the irrigation canals and river branches that hasn't fully dried out by mid-winter.
Also, don't assume that "sunny" means "warm." In the high desert of Eastern Idaho, the clearest days are usually the coldest. That's because there's no cloud cover to trap the earth's heat at night. If you see a perfectly clear 10-day forecast in January, prepare for your pipes to freeze.
Actionable Steps for the Week
Check your antifreeze levels today. With those overnight lows hitting 13°F and likely dropping into the single digits by next week, your vehicle's cooling system needs to be up to par.
If you are traveling North toward Rexburg, keep a small bag of sand or salt in your trunk. The blowing snow across the flats between Rigby and Rexburg can create "black ice" even when it hasn't snowed in days. The wind just picks up the old powder and polishes the road until it's a skating rink.
Keep an eye on the barometer if you're a local farmer or gardener. A sharp drop usually means those "few flakes" on Friday might turn into a real system. For now, enjoy the sun, but keep the heavy parka by the door.