The transition from summer to fall has felt more like an extension of summer than a true autumn cooldown. Since the start of September, above-average days have dominated the forecast, outnumbering below-average days by a remarkable 33to 14. That's not even close, and it's a trend that is set to continue here in northern Illinois and southern Wisconsin, with frequent stretches of warm afternoons keeping jackets on standby well into October.
"Big Bubble, No Trouble":
That warmth is likely to stick around a while longer. The "big bubble, no trouble" area of high pressure parked over the plain will gradually expand into the Great Lakes over the next few days. As it does, it will keep storm systems and the more active jet stream to our north, allowing sunshine, dry conditions, and above-average temperatures to remain the dominate story here as we approach October's end.
Look for patchy fog early this morning, but once it lifts, we'll be treated to plenty of sun for the rest of the day. Winds will remain light out of the southwest, helping temperatures climb well above where they should be for late October. Afternoon highs will reach the low 70s, running 10 to 12 degrees above average and making for another beautiful day.
There could be some patchy fog to start the day off tomorrow. However, any fog that develops should quickly let up shortly after sunrise, giving way to another day filled with sunshine and perhaps a few fair-weather cumulus clouds. Much like today, a light southwest breeze will help temperatures climb above late-October standards, with afternoon highs once again reaching the low 70s. Enjoy!
Chatter about this year's Super El Niño and how that will influence our winter season has been loud across social media. First off, we need to talk about what El Niño is. It is a weather pattern caused by warmer ocean waters off the coast of South America. When you hear "super" El Niño, that is referencing when sea surface temperatures in that region are 2.0°C above normal. This year, that intensity will be more than 3.0°C above normal, not necessarily that our local temperatures will be that far above average.
A typical El Niño pattern often results in milder than average temperatures, with around normal precipitation amounts. The warmer waters off the South America coastlines often push the Pacific jet stream along the Southern parts of the country, while the Polar jet takes a more Northwest track. This could limit the number and strength of big winter storms but may lead to an increase in quicker moving clipper systems from the Northwest.
How do our past El Niño winters compare to average? Meteorological winter runs from December 1st through February 28th, so all of these numbers below are averages across that time span. Typically, Rockford's normal winter will bring an average temperature of 24.2 degrees with 4.76" of measurable precipitation, and 29.2" of snowfall.
Two years in which the El Niño strength is comparable to this year were the winters of 1997-98 and 2015-16. In 1997-98, that winter saw a warmer than average trend with about normal precipitation and below average snowfall. The winter of 2015-16 saw another warm winter with below average snowfall. A simple analog forecast may come to a similar conclusion, but there are other factors that go into a winter forecast besides just what stage of El Niño we are seeing. But when El Niño is this strong, it may become the more dominant overarching pattern.
The National Oceanic and Atmospheric Association (NOAA) has put out their winter forecast, which closely resembles a typical El Niño pattern. Locally across the upper Midwest, we will likely see a warmer than average winter with equal chances of above average or below average precipitation. How that translates to individual snowfall events is not a direct correlation, so we will likely still see several instances of snow, potentially some heavy at times. But the frequency of those storms may be a bit lower compared to historical averages.
My personal forecast for Rockford this winter 2026-27 is that we will see above average temperatures, near average to just below average precipitation, and below average snowfall. But again, I want to emphasize that the 3.0°C above average you read about is NOT correlated exactly to what we will see locally.
It is also worth noting that Rockford has not seen a "typical" season of snowfall since the winter of 2020-21. Every winter since then has been below average, with the highest season of snowfall during that time receiving just below 20" of snow during the winter of 2023-24. Snow lovers may again have to wait another winter before we see abundant snowfall.
Did you know a super typhoon and a major hurricane are essentially the same type of storm? The biggest difference is where they occur across the world and the naming/classification being used.
Hurricane: Atlantic and eastern/central Pacific Ocean
Typhoon: Western Pacific Ocean
Both are tropical cyclones that strengthen using the heat from the warm ocean waters.
In the Atlantic and eastern Pacific basin, a major hurricane is any hurricane that reaches category 3, 4, or 5 status on the Saffir-Simpson Scale, with sustained winds of at least 111 mph.
The Joint Typhoon Warning Center (JTWC) classifies a tropical cyclone as a super typhoon when its 1-minute sustained winds reach 150 mph or greater. Putting it into hurricane terms, a super typhoon would be equal to a strong category 4 hurricane.
We've reached that time of year when temperatures can swing quite a bit throughout the day. You'll likely start the morning with readings in the 40s, making a light jacket or sweatshirta good idea as you head out the door. But with plenty of sunshine expected today, temperatures will warm rather quickly through the morning and climb into the upper 60s and low 70s by the afternoon. In other words, you'll be peeling off that extra layer pretty quickly.
Large Swings Continue:
In fact, those large temperatures swings will be the talk of the town over the next several days. A "big bubble, no trouble" area of high pressure parked over the Great Lakes will keep conditions quiet, with each morning starting off in the 40s before afternoon highs climb back into the low 70s. And just like today, each day will feature a good deal of sunshine thanks to the sinking air associated with this high pressure system. Typically, that limits cloud development.
Next System:
Forecast models do show some changes arriving as we head into the weekend. An area of low pressure tracking near the U.S - Canadian border Friday into Saturday will tighten the pressure gradient and lead to increasing winds, making for a breezy start to the weekend. The system's associated cold front will approach on Sunday, brining our next opportunity for a few showers late in the day.
We experienced our first frost and freeze of the fall season over the weekend as temperatures early Saturday morning dipped down around 30 degrees in many locations. Rockford fell to 31 Saturday morning and 36 Sunday morning. But afternoon temperatures warmed nicely this weekend - reaching the upper 50s Saturday and low to mid-60s Sunday. Monday was very similar - falling to 35 degrees in the morning and warming to 69 degrees for the afternoon.
These big swings in temperatures aren't anything new during the fall season and tend to be quite common, especially when dry air and sunshine are in an abundance. That's because dry air heats up much more efficiently than an air mass that has moisture in it. This means that temperatures could climb 30 degrees (or more) from where they start out at in the morning to where they end up at during the afternoon. As the days get shorter, though, those large temperature swings will become less frequent.
Overnight lows this week won't be quite as chilly as they've been the last few nights thanks to a little more of a light southerly breeze. This will keep our lows in the upper 30s to low 40s. Afternoon highs will warm into the low 70s through the weekend. Average highs by the weekend/early next week will fall through upper 50s.
October has been much quieter in the rainfall department compared to September. Last month, the Rockford Airport recorded measurable rain on 13 different days, helping make it a consistently wet month. So far in October, we've only picked up measurable rain on five days. Despite the drop in rainy days, many locations remain near to slightly above average for monthly precipitation thanks to the heavy rainfall at the start of the month.
Dry Pattern Continues:
We'll remain dry as we head through the start of the week. Amore active jet stream will stay well to our north, while areas of high pressure anchored over the Great Lakesand central plains keep systems away from the Stateline. As a result, sunshine will continue to dominate, though a few passing clouds may drift through this afternoon. Even with those occasional clouds, temperatures will climb into the upper 60s, making for a pleasant start to the week.
With a ridge of high pressure continuing to build across the central plains, the dry stretch looks to remain firmly in place through the rest of the workweek. Tuesday, Wednesday, Thursday, and Friday are expected to remain rain-free as storm system track well north of the area.
In fact, Tuesday and Wednesday could see wall-to-wall sunshine, helping afternoon highs climb into the upper 60s and low 70s each afternoon.
Weekend Sneak Peek:
Not much changes as we head into the weekend. However, forecast models continue to hint at a storm system developing across the plains as we head into Sunday. That may be enough to push a cold front northern Illinois and southern Wisconsin, bringing at least a slight chance for a passing shower.
At this point, moisture appears limited and rain chances remain quite low. Looking further ahead, our next more meaningful opportunity for precipitation may not arrive until the end of the month, possibly into the beginning of November.
It was a short-lived cool stretch over the last few days, especially with the frosty mornings of late. But the early fall chill will be in the rear-view mirror over the coming days, with many milder afternoons featuring highs in the 70s as early as Tuesday!
That warmer stretch looks to stick around for a bit longer into the end of the month, as the Climate Prediction Center gives a 70-80% chance that we would see above average temperatures persist between the 24th-28th! Average for that time of year would indicate highs in the upper 50s, so we will likely see more 60s and 70s a bit longer.
This also comes with a dry stretch. The next 7 days feature very little if any rain potential area-wide, and we continue the below typical precipitation chances into the last week of October as well.
But pattern changes are bound to happen especially when you get later and later into fall. And we are likely to see our next swing the opposite direction right after this time period mentioned from the CPC outlooks. Much deeper troughing in the jet stream will drop out of the Pacific toward the last couple days of October, with more frequent waves reaching us locally by early November. That will likely indicate more chances for rain and notably cooler stretches too.
November is one of the months that features the biggest change in typical weather from beginning to end. On November 1st, the average high is 55 degrees. But that drops to 40 degrees by the 30th. November also typically features our first measurable snow of the season, too! Rockford typically sees its first snow by November 19th.
