September's scorching start gives way to a cooler change

Late-Summer Heat:

We've seen quite the heat to start September across the Stateline, and it's already making a noticeable mark in the record books. In fact, we are now well-above average when it comes to 90-degree days for the month as Rockford on average sees just one 90-degree day during September, but last week's late-summer heat wave delivered 4 of them all by itself. That recent stretch of hot weather has also pushed our yearly total for 90° days up to 17.

What's Ahead?:

Looking ahead, the weather pattern is set to do a complete turnaround from last week's heat. After we saw 4 days in the 90s and several afternoons feeling more like mid-summer than early-September, we're in for an extended break from the warmth. 

Afternoon highs throughout much of this week will settle back into the upper 70s and low 80s, nowhere close to the 90-degree mark. Along with the cooler temperatures, we'll also be keeping an eye on a couple of cold fronts that could bring opportunities for rain and thunderstorms. The first arrives Tuesday night into early Wednesday, with another system expected to move through Friday night into Saturday, offering additional chances for wet weather as we start the weekend. 

Low Severe Risk:

As for our next chance for thunderstorms, the setup Tuesday night comes with a very low risk for severe weather across the Stateline. While a few stronger storms can't be completely ruled out, the potential remains highest to our west and north. The Storm Prediction Center currently highlights much of Iowa, southeast Minnesota, and a large portion of Wisconsin in a Marginal Risk (level 1 of 5) for isolated strong to severe thunderstorms. The primary threats in those areas would be gusty winds, but by the time storms approach the Stateline late Tuesday night, they will likely be in a weakening phase as they encounter a less favorable environment.     

Warm but pleasant Labor Day, rain chances return mid-week

 Labor Day will be a comfortable and pleasant one for those enjoying outdoor activities! Morning temperatures will begin in the 50s, but sunshine will quickly warm things up. Afternoon highs will reach into the lower 80s with a partly cloudy sky. But more notable, dew point temperatures will settle in the 50s with a much more comfortable air mass around!

Our next weather system will bring a Northward tug of moisture and humidity again between Tuesday and Wednesday, producing the chance for some showers and storms beginning late Tuesday evening and overnight. Any storms will be in a weakening state but could bring some gusty winds and small hail within the strongest cells. Another return of comfortable air filters in behind this system, with pleasant weather expected again Thursday and Friday.

Cooler nights ahead, patchy fog possible

 Temperatures are falling much faster than the last few nights, with overnight lows that will reach down in the low 60s. Under a lighter wind, a few patches of fog will be possible, with some pockets of locally dense fog in low-lying areas.

Tonight is just the start of a few cooler nights, with overnight lows in the upper 50s to low 60s. Much more comfortable air will be with us through the holiday weekend, as dew points remain below the 70-degree mark until Tuesday. Patches of fog will be possible at least Saturday and Sunday nights with high pressure and a lighter wind overhead.

Labor Day weekend still summer-like, but much more comfortable

 After Friday recorded a 4th straight day in the 90s to kick off September, the holiday weekend will not be quite as hot. The main reason for this will be the decreased humidity. High pressure will spread across the Great Lakes region, working to push the humid air mass back West again for a few days. This will send dew points down into the 60s, a much more comfortable feel than the mid and upper 70s from earlier in the week.

That will result in a much more pleasant, but still warm, forecast for this Labor Day weekend. Air temperatures may still push into the mid-80s Saturday, but lower 80s on the way for Sunday and Monday. Overnights are even more reflective of the less humid air, with lows in the 60s most nights! The lighter wind amid high pressure may result in a few nights of patchy fog, though. Lacking more sufficient moisture and upper-level dynamics, we will remain dry through at least Monday.

Friday night lights: Hot and humid with isolated thunderstorms possible

 [11PM] The bulk of our thunderstorms have now pushed well off to the East, resulting in drier conditions locally. While an isolated shower or storm remains possible into the night, most will stay dry. Humidity does not go anywhere, with temperatures only dropping into the low 70s. Patches of fog may be possible early Saturday morning.

[8:55PM] The storm has lost a bit of its strength but may still produce a quick burst of heavy rain and a strike or two of lightning as it moves overhead. Motion is still to the Southeast at around 30 mph.

[8:35PM] There have been a few more lightning strikes on this cell near Durand/Pecatonica in just the last few minutes. Storm is moving Southeast at around 20-30 mph, which could put it near the NW side of Rockford around 9PM if it holds together.

[8:30PM] A couple of isolated showers have developed near the Stateline. One moving into Northern Winnebago County that recently produced a lightning strike near Durand, and another in Western McHenry County. Both cells are moving Southeast at 20-30 mph.

[7PM] Thunderstorms have struggled to maintain themselves into the Stateline, with only a few stray showers surviving into Jo Daviess County. The clouds will continue to push across the area, with an isolated rumble of thunder possible from time to time, but most will stay dry this evening.

It will be another hot and humid evening with isolated storm chances! As of 4:30PM, many locations are seeing temperatures in the 90s with heat index making it feel like the triple digits. Isolated storms have begun developing to the Northwest, but are only moving at 20 mph.

If those storms maintain their strength, they might approach the Stateline after 6PM. Highest storm coverage may remain North of Rockford, but we will maintain a 20% chance through the late evening.

Either way, it will be rather humid start for those Friday night football games, whether they start at 7PM or are delayed to 8PM. Temperatures will remain in the 80s through at least 9PM where storms do not cool things down. Isolated storms remain possible through this time, but highest coverage will remain mainly North of the Stateline.

Continued dangerous heat Friday with some relief through the weekend

 

Heat and humidity will unfortunately stick around for another day here across the state line with the 4th day in a row of 90° temperatures on tap. Dewpoints won't offer any relief either as temperatures will be in the low 70's which will send heat advisories near and above 100° once again today. Because of this, heat advisories are in effect through 10pm this evening so make sure to continue to practice heat safety once again.

Thankfully, some relief does look likely into the weekend thanks to a higher-pressure system that's expected to move in by Saturday. This high pressure will be making its way out of Canada so as it makes its way south, drier and cooler conditions from the north will be dragged down to the Great Lakes region.

Temperatures over the weekend will drop below the 90° mark however we'll still be above average with temperatures each day. Either way, conditions should become more comfortable through the weekend thanks the higher pressure which should offer great conditions for Labor Day Festivities!

 

Dangerous heat continues: Third straight heat advisory in effect

Sizzling September:

It's been a sizzling start to September across northern Illinois and southern Wisconsin, with summer refusing to loosen it's grip. Tuesday brought one of the hottest days of the year so far, as Rockford soared to 96 degrees under strong sunshine and a persistent southwesterly wind. Adding to the discomfort, both September 1st and September 2nd featured peak heat index values above 100 degrees. 

3rd Heat Advisory:

With the heat continuing, a third heat advisory has been issued for all of our northern Illinois counties. Unlike the previous two advisories, this one is a bit longer-lived, having gone into effect this morning and remaining in place until 9PM this evening. 

 

Toasty Thursday:

Afternoon temperatures will once again climb into the upper 80s and low 90s, while humidity levels push heat index values into the 100 to 105 range. With another day with dangerous heat expected, make sure heat safety remains a HUGE priority. If you'll be spending an extended time outdoors, be sure to stay hydrated, drink of water, and take frequent breaks in the shade or air conditioning.  

Now, the one thing that could "spare" us from the heat would be thunderstorm chances which we have this morning and then again this evening into tonight. Like yesterday however, the jet is oriented in a way where the highest potential is displaced to our north across portions of Wisconsin, hence the level 2 Slight Risk for scattered strong storms. Roughly two-thirds of southern Wisconsin and most of northern Illinois are under a level 1 of 5 Marginal Risk for severe weather, indicating that any threat for stronger storms locally will be more isolated in nature.