Freeze warning issued for all of northern Illinois

Blustery Friday:

Strong winds will be the story today, and they'll play a big role in ushering in a much colder air mass for the start of the weekend. Northwest winds to start will gradually turn northerly by this evening, gusting up to 25 mph early before increasing to 30 to 35 mph this afternoon. The persistent wind will keep temperatures in the low 50s despite any sun. A few showers may accompany today's gusty wind as the storm system from yesterday continues to pull away. 

Frost Likely:

Winds will begin to ease this evening while staying out of the north and northwest overnight. Combined with clearing skies and a fresh surge of chilly air, temperatures will tumble to their coldest levels of the season thus far by Saturday morning. Many locations are expected to wake up in the low 30s, making it feel much more like mid-October.  

This colder air will also bring the likelihood for frost by Saturday morning. Because of that, the National Weather Service has placed the entire area, including our three counties up in southern Wisconsin, under a FREEZE WARNING. For northern Illinois, this will be in place from 5AM-8AM. Temperatures will be cold enough to damage or kill sensitive vegetation if left unprotected. Before heading to bed this evening, be sure to bring any potted plants indoors or cover them up to protect them from the frost. 

Weekend Outlook:

The rest of the weekend looks dry, with temperatures gradually warming after the chilly start. Despite lots of sunshine on Saturday, highs will remain stuck in the 50s thanks to the cooler air in place. By Sunday, winds will shift to the southwest and begin to pick up a bit, helping temperatures climb back into the low to mid 60s. The warming trend continues into Monday, when highs could approach 70 degrees. 

Cold and blustery Friday, hard freeze possible Saturday morning

 Rain showers will continue to linger through the evening Thursday, but some drier air will bring an end to the steady rain after 9-10PM. As the "dry slot" of the system passes overhead, coverage of rainfall will wane. But winds will pick up, with Northwest gusts approaching 30 mph at times.

Temperatures will fall to the 40s to start out the day Friday but won't warm much from there with a stout Northerly wind. Afternoon wind gusts could push 30-35 mph, which will limit high temperatures to the low 50s. A few light showers will be possible from time to time, but only a couple tenths of an inch of additional rain will be possible.

Winds will ease substantially overnight into Saturday morning, but temperatures will continue to fall under the influence of high pressure. By daybreak, most will be in the low 30s with potential for the first hard freeze of the year. A freeze watch is in effect for far Northwestern Illinois and Southern Wisconsin. Be sure to protect any sensitive plants from the likely frost and freezing conditions!

Wet Thursday ahead, frost threat looms by Saturday morning

Wet Thursday:

After a stretch of dry weather, you'll want to keep the rain gear handy on Thursday. A seasonably strong area of low pressure moving into Illinois will bring the chance for isolated showers during the morning hours, but the wetter part of the day arrives later on. Rain coverage is expected to become much more widespread by midday, with periods of steadier and occasionally heavier rainfall continuing through the afternoon and evening. 

If you have to be out and about, be prepared for wet conditions, allow for extra travel time, and keep an umbrella and rain jacket nearby. While temperatures won't be especially cold, the combination of the rain, the cloud cover, and east-southeast wind will limit afternoon highs to the low 60s. 

Most locations should pick up a beneficial rainfall from this system, with amounts generally from 0.25" to 0.75" by the time chances end.

Cooler Times Ahead:

Scattered showers will linger through the first half of the night Thursday, before tapering off behind the associated cold front. In the wake of this cold front, winds will increase and usher in a quick shot of much cooler air. Temperatures are expected to tumble into the low 30s by Saturday morning, allowing frost to be likely. If you still have sensitive outdoor plants, be sure to bring them indoors or cover them up before heading to bed Friday evening.

Strong fall system to bring widespread rain, then fall chill

 A seasonably strong weather system will push through the Stateline before the weekend, bringing widespread rain then a sharp cool down between Thursday and Friday. We will start off Thursday with pockets of light to steady rain, lasting through the duration of the day. There is potential for some pockets of heavier rain embedded within, where some may pick up an inch of rain. The tail end of the system will likely wrap additional showers through the area, but not as widespread as Thursday. Winds will be much stronger from the Northwest or North, holding temperatures in the 50s with frost potential overnight into Saturday.

The initial push of rain will arrive after 5-6AM, with scattered and light showers at first. Through late morning and early afternoon, coverage will become more widespread with pockets of moderate or even heavy rain. That band of heavier rain will be fairly narrow on the Northern edge of the low pressure, resulting in more sporadic rainfall coverage over parts of Northern Illinois. Where that narrow band sets up will bring better chances for the soaking rain of up to an inch.

Additional wrap-around showers will be possible into Friday afternoon with more subtle moisture rotating around the center of the low-pressure system. This will also be accompanied by stronger Northwest to North winds, gusting around 30 mph or greater at times. Temperatures may struggle to reach the 50s in a few spots during the afternoon and continue falling at night, down into the 30s. It does appear increasingly likely that we will see our first frost of the season Saturday morning!

Rain returns Thursday, frost possible by Friday night

Quite The Drop:

Monday's record-breaking high of 88° is feeling like a distant memory. A cold front and departing storm system have helped usher in a much cooler air mass, sending temperatures back to where should be for the middle of October. Instead of flirting with records, afternoon highs will top out near 67°, much closer to seasonal averages. We're also trading yesterday's sun for a bit more cloud cover as clouds look to linger behind the departing storm system. 

Thursday's Rain:

From there, the forecast turns a bit more unsettled as another area of low pressure lifts into Illinois from the southwest. Rain chances increase shortly after midday Thursday, with widespread showers, possibly a few thunderstorms, expected through the afternoon and into the early evening hours. 

 

Conditions gradually dry out Thursday night, though winds will become quite gusty behind the departing system, helping pull in cooler air. Overnight lows are expected to fall into the low to mid 40s by Friday morning, with even colder temperatures arriving by Friday night. In fact, lows are expected to drop into the low to mid 30s, which could bring the potential for frost across parts of the area. Keep tabs on the forecast as you might have to cover sensitive outdoor plants before heading to bed Friday. 

As for rainfall totals, most locations should pick up between a quarter to three-quarters of an inch, though a few spots could wind up near 1". A strong area of high pressure will push in for the weekend, keeping us dry but chilly with highs in the 50s.  

 

  
 
 

Frost/freeze potential in northern Illinois Friday night

 

We've enjoyed quite the stretch of mild and mostly dry fall weather over the last week to week and a half, but a return back to reality and more of an 'October-like' feel will greet us by the end of the week.

For the remainder of Tuesday evening, we'll see a mix of sun and clouds as a few weaker upper-level disturbances move across the Midwest. A couple of those disturbances have produced a few showers and thunderstorms west and south of the Stateline. The shower activity across central Illinois isn't anything we need to be concerned with and will mainly remain to the south. But the cluster of thunderstorms moving through northeast Iowa will continue on their northeast trek, reaching southern Wisconsin around 7pm-8pm. Additional isolated thunderstorms will remain possible across northern Illinois after 8pm-9pm.

Wednesday will feature more clouds than sun which will hold afternoon temperatures in the mid-60s. Winds will turn to the north and northeast. Widespread rain returns Thursday with increasing moisture and low pressure sliding just to our south. Northern Illinois will remain north of the low which will keep afternoon temperatures in the 50s and low 60s, but south of the low (in the warm sector) afternoon temperatures will climb into the 70s and 80s.

Following the passage of the low a strong cold front will sweep across the Midwest and western Great Lakes Friday morning. This will pull a considerably cooler air mass down into the Stateline Friday afternoon. Afternoon temperatures will fall through the 50s, remaining in the 50s, during the afternoon. This will also come with a rather strong north wind with gusts 30-40 mph. Following some of the record heat from Monday afternoon it will feel rather chilly Friday afternoon.

By Friday night the winds will ease some as high pressure slides a little close to the Stateline. This will cause temperatures overnight Friday into Saturday to plummet down into freezing territory Saturday morning. This could lead our first fall frost/freeze this season.

As the mercury drops it'll be pretty much right on target for when we typically average our first fall freeze, which for Rockford is around the 13th of

October. Last year the temperature fell to 30 degrees on October 23rd. The earliest fall freeze was back on September 13, 1975, and the latest was the 11th of November back in 2016.

Warmth fades as rain chances rise later this week

Rainfall by Month:

While October hasn't been especially wet overall, the rain we picked up on the very first day of the month has done a lot of the heavy lifting. That early-soaking rain was enough to keep rainfall totals running above-average, even as we've settled into a remarkably dry and sun-filled stretch since then.  

 

Few Evening T-Storms:

Rain chances begin to increase from here, but not before one more mainly dry day. In the wake of this morning's cold front, skies will remain partly cloudy with afternoon highs landing in the upper 70s, close to the 80 degree mark. While this is a step down from the record-breaking warmth we had yesterday, it's still above mid-October standards. 

The cold front from this morning along with upper-level support being filtered in from the southwest will help stir up a few showers and thunderstorms this evening into the first half of tonight. IF we end up seeing a severe thunderstorm, large hail would be the primary concern. Overall, the better chances for rain seem to remain south of Rockford, mainly along and south of the I-88 and I-80 corridors. Coverage should gradually diminish after midnight, with activity becoming a bit more isolated. 

Rain Likely Thursday:

By the morning commute Wednesday, any lingering rain will have move out, but clouds will be slow to clear the Stateline. In fact, mostly cloudy skies are likely to stick around for much of the day. Combined with a cool east-northeast breeze, afternoon highs will be limited to the upper 60s.    

A low-pressure system arriving Thursday will bring our next significant chance for rain, along with the potential for a few thunderstorms. The greatest coverage appears likely during the afternoon and evening hours as deeper and rich moisture moves into northern Illinois and southern Wisconsin. While the details are still being fine-tuned, many areas may see a beneficial rainfall with the heaviest right now trending to the south. Because of the rain pushing in during peak-heating hours, afternoon highs will be limited to the low 60s.