Extremely cold arctic air plunges into northern Illinois following a very mild Friday

Thursday was the warmest day of 2025 so far as highs reached the upper 30s. A drastic change from how we started out the work week. 

However, that title reign will only last a day as Friday features even warmer temperatures. 

 

 

Clouds early in the day should mix with a bit more sunshine by the afternoon. That, along with an increasing wind out of the southwest will allow highs to climb into the low to mid 40s.

Enjoy every second of today's warmth because once a pair of strong fronts sweep through, we'll be taking a trip back to the Arctic circle. 

 

Temperatures by Saturday morning will end up in the teens, only climbing a degree or two for the afternoon as winds blow out of the northwest. Overnight, we'll fall into the single digits and remain in the single digits throughout the day Sunday. Wind chills Sunday will likely stay below 0° all day, landing in the -20° to -25° range by Monday morning.  

 

 

The core of this Arctic blast arrives Monday and Tuesday, leaving highs closer to the 0° mark. Winds will make matters worse, leaving chills in the -15° to -20° range Monday afternoon, with values falling to the -20° to -25° Monday night. 

The equates to frostbite occurring in 15 minutes. If you can, avoid being outdoors for a prolonged period of time. If you can't cover as much exposed skin and dress in as many layers as possible. 

Polar vortex to bring sub-zero wind chills next week

Our next outbreak of bitterly air will arrive next week, plunging temperatures well below average for a time. But where does this cold air come from? It has an Arctic origin near the North pole! A polar vortex will help draw that air mass our direction through the weekend and into next week, bringing dangerous cold our way. The air mass will have bitterly cold temperatures down at the surface, but even colder air higher in the atmosphere. 

Roughly a mile up, the air temperature will be near -20°! If you see maps showing 850 mb temperatures, this is the layer of air that typically denotes whether the surface will be mild or cold.

The surface temperature will also dip below zero for a period of time, but not quite as cold as the air further aloft. Our forecast temperatures early next week show highs in the single digits and lows down below zero Sunday and Monday nights!

Those temperatures are not counting the wind chill, though. With blustery winds on the leading edge of the arctic air Saturday and Sunday, wind chills will be well below the air temperature, and below zero starting Saturday night. The lowest wind chills will be Sunday and Monday nights, when chills could approach -25°. Wind chills will remain below zero likely though early Wednesday.

With wind chills as low as they will be, frostbite can set in quickly. When the wind chill is between 0° and -15°, frostbite is possible within 20-30 minutes on exposed skin. When the chills are -15° to -25°, frostbite can set in within 10-20 minutes. Be sure to bundle up and cover exposed skin if you must be out in the cold next week!

Brief warm-up continues Friday

 

Despite the northwest wind Thursday afternoon temperatures were still able to warm well into the 30s, reaching the upper 30s area wide. Unfortunately, the wind did make it feel roughly 10 degrees cooler. Winds will continue to ease through the night before ramping up shortly after sunrise Friday.

The 'warm-up' will continue into Friday as southwest winds take hold bringing temperatures into the low 40s. However, wind gusts will top 30-35 mph which will, again, make it feel roughly 10 degrees cooler during the afternoon.

A strong cold front racing in from the northwest Friday evening will quickly shift winds around to the northwest, bring temperatures from the 40s during the afternoon down into the upper teens Friday night. Gusty northwest winds will continue into Saturday morning pushing wind chills into the low single digits, with chills not warming much during the afternoon.

Precipitation chances remain limited locally with the front Friday, staying further to our southeast during the afternoon and evening. In fact, precipitation chances will remain rather limited throughout the weekend as a strong Arctic high pressure system moves in Saturday and Sunday.

The Arctic high will push a series of cold front through the Stateline, each one bringing temperatures down through the beginning of next week. Highs on Saturday will only warm to around 20 degrees, but then drop into the single digits (yes, single digits) for Sunday! The cold will last through at least the middle of next week. 

Brutally cold Siberian air filters into northern Illinois next week

If you though last week and this week were cold, just wait till early next week. 

A powerhouse of a cold front will pass through the western Great lakes Friday into Saturday, plummeting temperatures across much of the lower 48. But where is this air coming from? 

Well, a product provided by NOAA called the hysplit model uses model data to track the path of certain airmasses. Next week's blast of extremely cold air has origins from the heart of Siberia. BRRRR!

Temperatures Saturday will top out in the low 20s, but that will be early in the day. Overnight lows will drop into single digits Sunday morning as the core of this Arctic blast begins to settles in. 

This will leave highs between Sunday and Tuesday in the single digits, with overnight lows landing below both Sunday night and Monday night. Factor in an organized wind, and it’s likely the Stateline will see wind chills as low as -20° to -30°.

Bitter cold to sweep through Northern Illinois next week

 While we have seen a few hits of Arctic air so far this winter, Rockford's coldest low of the season was 0° Wednesday morning. After a brief warm-up late in the week, even colder weather will arrive next week. Afternoon high temperatures will struggle to reach out of the single digits Sunday through Tuesday, with overnight lows solidly below zero Sunday and Monday nights.

That is just factoring in the air temperature, though. With the wind chill taken into account, it will feel closer to 20 or 25 degrees below zero at times! Minimum wind chills could reach negative 15° Saturday, then -25° Sunday and Monday. This is just an estimate range of possible outcomes this far out, but it is looking very likely wind chills will reach at least 20 below at times. If we see widespread wind chills near -20°, we could see our first ever "Cold Weather Advisory" issued by the National Weather Service.

This cold air will begin to arrive Friday night and Saturday morning. The timing of that cold air could coincide with some moisture streaming up from the South. This may allow for some wintry mix, including rain and snow, to fall during that time. The exact timing of the two features is still uncertain a few days out, but there is a chance for some wintry precipitation Friday into Saturday before the coldest air arrives Saturday night through Tuesday.

Scattered snow showers Wednesday evening

 Our next weather system is currently producing scattered snow showers off to our Northwest, in portions of Minnesota, Iowa, and Wisconsin. This "clipper" system will pass through the Stateline over the course of Wednesday evening, providing some quick bursts of snow locally.

Snow could start by 7PM for some of our Northwestern communities, with many in the Stateline seeing scattered snow showers by 9PM. These quick bursts of snow will reduce visibility for a period of time and could provide a quick coating of snow especially on untreated surfaces. Steady snow showers will move out toward midnight, with a few flurries lingering into Thursday morning.

All told, accumulations will likely remain below 0.5" but that could be enough to cause some slick spots on roadways and untreated surfaces through the late evening. Highest totals will likely remain well to the Northeast, closer to the surface low pressure system producing this snow.

Short-lived warm up, with another blast of Arctic air arriving this weekend

Sub-zero wind chills greet us out the door one more morning before relief settles in. 

Our the door, expect temperatures to be hovering on either side of the 0° mark, with wind chills possibly ending up as low as -10°. Southwest winds pick up on the backside of a departing high pressure system, bringing afternoon highs into the low 20s.  

At the same time, our next weak disturbance will be on approach, increasing cloud cover prior to the evening commute. Not too long after do forecast models introduce our next chance for snow. This round will be quick to move in and quick to move out, with the highest potential for minor accumulations occurring from 8PM-2AM. In a similar fashion to Tuesday morning's snowfall, tonight's snow will be scattered in nature, leaving behind a trace to .5". Keep an eye out for slick spots if you plan to travel Thursday morning.

Behind this disturbance, surface flow will turn back to the northwest. Despite this however, the upcoming warming trend will be in full swing, landing afternoon highs above freezing in the upper 30s.  

Friday is the warmest day the Stateline has seen since December 29th where we topped out at 44°. Winds turn warm and breezy out of the southwest, allowing afternoon highs to jump to the low 40s.  

Enjoy every single second of it because as we've been hinting at, this stretch of above-freezing temperatures is here for a brief visit. A stronger cold front sliding through early Saturday will help a much larger dose of Arctic air spill into the lower 48. 

 

 

Temperatures fall during the day on Saturday, leaving us in the single digits Sunday morning. 

Afternoon highs to round out the weekend barely make it into the teens, falling below zero overnight. M.L.K Jr Day on Monday will end up being the coldest day of the winter thus far. Afternoon highs only top out in the single digits, with overnight lows once again falling below zero.