We mark a solemn anniversary Monday. It was 33 years ago, at 3:45pm August 28, 1990 that the catastrophic PLAINFIELD TORNADO—the only “F-5” intensity tornado to sweep the U.S. in August with its estimated 261 to 318 mph winds— barreled along a 16.4 mile trek, running from the Fox River at Oswego through Crest Hill and into Joliet. 

It leveled Plainfield high school, 470 homes—damaging 1,000 others– and destroyed a Crest Hill apartment complex.  School would have begun only a day later at Plainfield High, where the football team practiced as the storm moved in.

When the storm had lifted back into the clouds over Joliet, it had killed 29 and left nearly 300 injured. It remains the most deadly tornado to strike Illinois in August.  Insidiously, the days tortuously high dew points (low 80s) and temps (in the low 90s) combined with a jet stream to produce the 64,000 ft. tall parent cumulonimbus cloud which could be see from Chicago proper, where an inland moving lake breeze had scoured the skies clear of clouds. The moisture saturated atmosphere wrapped the twister in a blinding veil of rains and clouds hiding it from sight.

No photo of the tornado itself has ever emerged. Only a College of DuPage storm chase team ever photographed the developing tornadic vortex over southern Kane County not far from Sugar Grove—home to Aurora Municipal Airport which had to be evacuated as the vicious t-storms which were to spawn the tornado over the Fox River at Oswego—swept southeastward.

Full forecast details and more at the WGN Weather Center blog

Movement of the storm from the northwest was unusual in and of itself for a tornadic t-storm since most move from the southwest in the early tornado season.  August t-storms often come in from the northwest. 

MOVING TO THE RECENT AND CURRENT WEATHER REGIM—-What a change from last week’s heat—including Wednesday’s record tying 100-deg high—only the 63rd official triple digit high temp here in 153 years of weather records. 

We’ve come off spectacular, eminently comfortable weekend weather and segued into a gorgeous open to the new week.  With just 3 days remaining in August and the meteorological summer season (both end at midnight CDT Thursday evening), the month of August is running a 1-deg surplus and at a level 0.7-deg warmer than the opening 28 days of the month last year.

The weekend, with temps of 77/63 Saturday and 75/61 Sunday ended up 8-degrees cooler than last weekend.

Monday continued the trend of beautiful weather with an official high likely to end up 81-deg after a morning low of 59.  

Some interesting weather looms. A warm Tuesday and the arrival of a cold front later in the day should initiate scattered t-storm development which is likely to take place across portions of the Chicago area in roughly the 10am to 6pm time frame.

Once that front passes, a  VIGOROUS NORTHERLY WIND FIELD LOCKS IN TUES NIGHT INTO WED—much like the one which whipped up impressive waves on Lake Michigan and limited daytime warming this past weekend.  Gusts near and out over Lake Michigan are likely to approach 30 mph—higher over the lake’s open waters.  Expected waves and rip-current to take shape.

Wednesday will have the feel of an early autumn day with highs approaching 70—more than 10-deg below normal.

Comfortable weather continues Thursday—BUT HOT AIR looms this weekend —and even more so over the coming weekend 

Current modeling builds an impressive late season dome of HOT AIR over the Midwest this weekend and into next week—likely just shy of the intensity of last week’s hot air—but WELL ABOVE NORMAL.  A string of 90+-deg daytime highs may commence Saturday and run through mid-next week—with moderate weekend humidity levels growing more humid next week.

The coming weekend could see highs of 94 and 97-deg Sat & Sunday and could average 14-deg hotter than this past weekend. THAT’S A POTENTIALLY BIG CHANGE!

While this week is likely to average a tad (perhaps 0.6-deg) BELOW NORMAL, the arrival of heat NEXT WEEK could send the weekly average temp to greater than 82-deg– a reading which could end up more than 12-deg ABOVE NORMAL.

ALSO—TROPICAL STORM “IDALIA” appears headed for MAJOR HURRICANE STATUS as it CHURNS NORTHWARD the abnormally warm waters of the Gulf of Mexico toward a northwest Florida peninsula landfall Wednesday night and/or early Thursday. The National Hurricane Center is indicating the storm is headed for “MAJOR” CAT 3 intensity with sustained winds of 115 mph. A storm surge is predicted to sweep into Florida’s Gulf Coast.



TONIGHT: Mainly clear, a bit cool but comfortable.  Low 59—with low to mid 50s cooler inland locations.

TUESDAY: Becoming partly cloudy and warmer. Some scattered 20 to 40% coverage showers and possible t-storms possible in the 10am to 6pm time frame.  Gusty “NNE” winds lock in late in the day dropping temps. High 84 falling back to the upper 60s to mid 70s by sunset.

TUESDAY NIGHT: Partly cloudy, windy and cooler. Gusts build 25 to 30 mph.  Low 61—but mid 50s inland.

WEDNESDAY: Early clouds thin out, becoming mostly sunny, fairly windy and cool by late August standards. High 69.

THURSDAY & FRIDAY: Generous daytime sunshine, much calmer with day to day warming—but with low humidity.  High Thursday 77—low 70s beaches. Friday’s high 88—only a few degrees cooler along the lake.

SATURDAY: Partly sunny, breezy and turning hot in the afternoon. Moderate humidities (dew points in the low 60s).  High 94.

SUNDAY & MONDAY: Mostly sunny and breezy with hot afternoons and moderate humidities.  Southwest winds are likely to defeat ANY lake cooling—so it will be hot up to and over area beaches and adjacent lake waters. High Sunday 97.  Monday’s high 96.