If you stepped outside in Sullivan this morning, you probably noticed the air felt a lot sharper than it did yesterday. Basically, the "warm" spell we had earlier this week is officially a memory. We’re sitting right in the middle of a typical Missouri January transition where the sky looks beautiful and sunny, but the wind is busy making you regret every life choice that led you away from your space heater.
The current weather forecast for Sullivan Missouri shows us hitting a high of about 40°F today, Wednesday, January 14, 2026. Sounds okay on paper, right? Wrong.
Those northwest winds are ripping through at 19 mph, with gusts reaching up to 35 mph in some spots. It makes that 40 degrees feel more like 25. Honestly, if you’re heading out to Meramec Community Center or just grabbing a coffee, you've gotta layer up more than you think. Tonight, the mercury is going to dive. We’re looking at a low of 20°F under a perfectly clear sky.
The Seven-Day Outlook: Teeth-Chattering Temperatures
It’s gonna stay cold. Actually, it’s going to get worse before it gets better. Thursday looks like a carbon copy of today with a high of 38°F, but Friday brings some drama. There’s a 20% chance of light snow Friday night as the temperature hangs around 43°F during the day and drops to 21°F after dark. Don't expect a blizzard, but keep an eye on the windshield for some slushy accumulation.
Then comes the real Missouri winter bite.
💡 You might also like: The Recipe Marble Pound Cake Secrets Professional Bakers Don't Usually Share
Saturday is going to be brutal. We’re talking about a high of only 27°F and a low that plummets to 9°F. Yes, single digits. If you have pipes that are prone to freezing or outdoor pets, Saturday night is your deadline to get things squared away. Sunday isn't much better with a high of 28°F. The wind chill values during this weekend stretch are expected to hover near or below zero, which is when things get legitimately dangerous for exposed skin.
By Monday, January 19, we’re still stuck in the freezer with a high of 22°F. It’s not until the following Wednesday that we see a glimpse of hope with temperatures climbing back toward 49°F. Missouri weather is moody like that.
Breaking Down the Humidity and Wind Factors
People always talk about the heat index in the summer, but in Sullivan, the winter humidity and wind are the real story. Right now, the humidity is sitting at about 39%, which is relatively dry for us. When it’s dry and windy, your skin loses moisture and heat way faster.
The wind is coming almost exclusively from the northwest right now. That’s a direct pipeline from Canada.
📖 Related: Why the Man Black Hair Blue Eyes Combo is So Rare (and the Genetics Behind It)
Historically, January is our coldest month for a reason. Data from the National Weather Service and projects like NASA’s MERRA-2 show that Sullivan usually averages a high of 41°F and a low of 22°F this time of year. We are currently trending a few degrees below those averages, especially as we head into the weekend. It’s not "record-breaking" cold yet, but it’s definitely "don't leave the house without a heavy coat" cold.
What to Expect Through the Rest of January
- Cloud Cover: We're looking at about 52% cloud cover on average this month. Friday and Monday will be the grayest days of the upcoming week.
- Precipitation: While the chance of snow is low (mostly around 10-20%), any moisture that hits the ground on Friday night will likely freeze solid by Saturday morning.
- Daylight: We're getting about 9 hours and 48 minutes of daylight. Sunset is currently around 5:08 PM, so the temperature drop happens fast once the sun dips.
Common Misconceptions About Sullivan’s Winter Weather
A lot of folks think that because we aren't in the "North," we don't get Arctic air. That's a myth. Sullivan sits in a spot where the Ozark plateau starts to influence things. We often get "cold air damming," where the heavy, cold air settles into the valleys and stays there longer than it does in St. Louis or even Franklin County's flatter areas.
Another thing? People underestimate the "feels like" temp. If the weather forecast for Sullivan Missouri says 30 degrees, but the wind is 20 mph, you are physically experiencing 17 degrees. That difference is the gap between a brisk walk and frostbite if you aren't prepared.
Surviving the Single-Digit Dip
If you’re planning on being outdoors this weekend, specifically Saturday and Sunday, you need to think about your car and your home. Make sure your antifreeze is rated for these temps. Missouri's "yo-yo" weather—where it’s 55 one day and 9 the next—is incredibly hard on car batteries. If your battery is more than three years old, this weekend might be the one that kills it.
👉 See also: Chuck E. Cheese in Boca Raton: Why This Location Still Wins Over Parents
- Check your tire pressure. Cold air makes the pressure drop, and you don't want a "low tire" light flashing when it's 10 degrees out.
- Drip your faucets. Especially if you have a north-facing wall, let a tiny trickle of water run Saturday night.
- Limit pet time outside. If it’s too cold for you in a coat, it’s too cold for them, even with fur.
Actionable Steps for Sullivan Residents Today
Check your supplies now. Don't wait until Friday afternoon when everyone is rushing to the store because they heard the word "snow." You don't need a bunker, but having an extra bag of ice melt for the driveway and making sure your space heaters are clear of curtains or furniture is just smart.
Keep an eye on the sky Friday evening. Even a light dusting of snow followed by Saturday's 9-degree low will turn I-44 into a skating rink. If you can stay off the roads Saturday morning, do it. The wind gusts will be high enough to make high-profile vehicles feel a bit "floaty" on the highway too.
Stay warm, keep the layers on, and remember that by next Wednesday, we'll be back near 50 degrees again. That’s just life in Missouri.
Data sourced from the National Weather Service St. Louis office and historical climate records for Franklin County.