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.

Isolated thunderstorms return late Tuesday night

 

Temperatures Tuesday won't be quite as hot as they were Monday, but they'll remain close to 80 for some into the afternoon. A cold front passing through the Stateline Tuesday morning will shift winds from the southwest to the northwest. There isn't much cold air initially behind the front which is why afternoon highs will remain above average.

Most of Tuesday will see dry, and likely, sunny conditions. But clouds will increase through the evening as a surge of moisture returns late Tuesday night. This moisture will arrive with increasing winds from the low-level jet (stronger winds a few thousand feet above the surface). The front from Tuesday morning will have settled to our south, sitting roughly across central Illinois. Showers and thunderstorms will develop after sunset (between 8pm and 11pm) across southern Iowa, moving towards northern and central Illinois around Midnight - and beyond.

The Stateline will sit on the northern edge of the thunderstorm activity, and north of the front, which will help keep the highest risk for widespread thunderstorms to the south. But a few of those thunderstorms could reach some of the region, mainly in the form of elevated thunderstorms. With just enough instability the strongest of the storms could produce some locally large hail (quarter of an inch, or greater) along with gusty winds late Tuesday night. Because of that risk the Storm Prediction Center has placed areas along and west of I-39 in northern Illinois under a 'marginal risk' for isolated severe storms. At this point it doesn't look to be anything too widespread, but something we'll need to keep an eye on heading into Tuesday night. 

Record heat for Rockford Monday afternoon

You may have had to do a double take when looking at the calendar this afternoon. Temperatures across northern Illinois and southern Wisconsin felt more like July or August and not the middle of October. That's because afternoon highs warmed well above the average high of 64 degrees, climbing into the mid and upper 80s! Rockford's high officially reached 88 degrees! That's 24 degrees ABOVE AVERAGE!

Not only is that warmth incredible for October it was also record breaking. The previous record for October 12th was 85 set back in 2008, as well as in 1930. On average, Rockford's last 85-degree recorded temperature (or higher) is around the 19th of September. Not only did today's high surpass that it is also the warmest temperature this late in the season since October 15th, 1947, when the high that day reached 89 degrees! Simply put - this type of warmth doesn't happen very often and is definitely rare.

We'll see a few clouds roll through the region through the evening with mostly clear skies expected for the night. Temperatures tonight will fall to around 66 degrees. A cold front will slide through the region Tuesday morning shifting winds to the northwest. There isn't much cold air behind this front initially, so afternoon highs are likely to warm back close to 80. But moisture surging north Tuesday night will likely lead to a few elevated showers and thunderstorms after Midnight, into early Wednesday.

80s in October? Record highs could fall across northern Illinois today

What's Ahead:

Remember when 90° heat was stealing the headlines at the start of September? Now, just a few weeks later, we're talking about possibly record-breaking warmth as we head into the middle of October. That's where this week's weather story begins! 

 

Record Warmth:

The reason for the potential record warmth today comes down to a favorable setup ahead of our next cold front. Conditions remain very dry across the region, and a strengthening southwest wind will help transport much warmer air into northern Illinois and southern Wisconsin. With plenty of October sunshine and little chances for rain, temperatures will have no trouble climbing into the mid 80s. That puts today's record high of 85° from 2008 in jeopardy.  

Forecast models continue to show our next cold front pushing through early Tuesday morning, but with very little moisture available, its expected to sweep through dry. We do on the other hand see a round of slightly cooler air push in behind it. However, we're still expecting temperatures to climb to mild levels, landing in the upper 70s. As for the record books, the standing record high for tomorrow of 87 degrees will remain intact for another year. 

Rain Chances Rise:

As we move into the second half of the work week, temperatures will begin to cool while rain chances start to increase. A surge of atmospheric moisture is expected to move into the region on Thursday, giving us the ingredients for showers. Heaviest seems to occur to the south of I-88, but it will be important to keep up with trends the next few days.    

Steady decline from record warmth to fall chill this week

 It was a warm weekend across the Stateline with 2 days reaching the 80-degree mark or warmer in Rockford. We will make it a streak with a 3rd day in the 80s Monday, with a forecast high of 85! That would tie a record high set in 2008. But it is all downhill from there, with afternoon highs dropping each day until we reach the 50s on Saturday!

This will come with a few chances for rain, notably with a chance for a few elevated storms Tuesday night. These will not be overly widespread, but a couple of the strongest storms may pose a low-end risk for some gusty winds and severe hail. The Storm Prediction Center has placed a Level 1/5 Marginal Risk over parts of West Central Illinois, up to around I-39/I-88.

Wednesday will be largely dry, but more widespread and steady rain will be possible Thursday with our last push of moisture before a strong cold front arrives. This could bring some pockets of 0.5-1.0" rainfall totals, with some locally heavy rain, especially South of I-88. Behind this weather system, much cooler and drier air will take over into the following weekend.