Tim's Weather World: Quick shot of fall then warm up

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It felt just like July yesterday with highs topping 90° in a few spots.   It hit 91° in Romeoville and 92° in Rockford.  A cold front coming through today will usher in much cooler Canadian air.  Highs this weekend will be nearly 10° below average.  Lows by Sunday morning may dip into the upper 30s well west and northwest of the city.  The timing of this autumnal air mass coincides well with the official start of fall on Sunday at 3:44 PM.



It doesn’t look like this cool down will last long.  We should be near 80° by Wednesday and be into the 80s by the end of next week.  The longer range (6 to 10 day and 8 to 14 day) forecasts from the Climate Prediction Center have us outlooked for above average temperatures overall through the end of the month and into early October (see above image).




Tim's Weather World: Soggy Sunday brings much needed rainfall

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Our soggy Sunday saw .65″ of rain fall at O’Hare.  That is the most rainfall in a calendar day in over two months.  The last time more rain fell during a calendar day was when .92″ fell on June 27th.  The graphic below shows the doppler radar estimated rainfall amounts from Sunday.  The heaviest rain fell just north and northwest of the city.

13Sept15ppHere are some other rainfall amounts for Sunday from our WeatherBug network:

1.05″   Mundelein

1.01″   Island Lake

.90″    Wheeling

.87″    McHenry

.84″   Morton Grove

.81″   Schaumburg

.81″   Buffalo Grove

This welcome rain fell just three days after the latest US Drought Monitor reported a deepening drought across the state of Illinois (see image below).  Just under 40% of the state was experiencing a moderate drought as of last Thursday.  3.58% of the state was in a severe drought.  That was a slight increase in both levels of drought compared to a week ago.   Sunday’s rainfall brought the total for the month at O’Hare to .80″ which is still .85″ below average.




Tim's Weather World: This summer was the 15th warmest on record

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The numbers have been crunched and it’s now official, this past summer was among the top twenty warmest for the contiguous US.  The average temperature for August was 73.1°, 1.0° above the 20th century average.  That ranks August the 28th warmest such month on record.  The average temperature this summer (June, July & August) for the contiguous US was 72.6°, 1.2° above the 20th century average.  That makes this past summer the 15th warmest on record for our country.




Some other highlights from NOAA’s report:






Tim's Weather World: Make it rain!!!

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We saw some much needed September rain yesterday but the overall numbers were pretty paltry.  Here are some of the rainfall amounts gathered from the National Weather Service and our WeatherBug network:


.33″ Hebron

.24″ Aurora

.17″ East Chicago

.16 Oak Lawn

Trace  O’Hare

Trace Midway


The latest numbers from the US Drought Monitor shows a slowly expanding drought setting in across Illinois.  The Chicago area is included in the nearly 66% percent of the state that is “abnormally dry”.  Just under 40% of the state is in a moderate drought and nearly 4% is in a severe drought.  The numbers have gone up slightly in nearly every category compared to a week ago.



Rainfall across the state is down anywhere from 1-4″ from normal for the past 30 days.  O’Hare is down 1.09″ for the month on top of a 3.21″ deficit from August.  There may be a few spotty showers late today and some lake effect sprinkles or showers tonight & tomorrow but not the soaking type of rain that is needed bring us back to average.





Tim's Weather World: More steamy September weather ahead

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Climatologically speaking, summer ended at the end of August but September didn’t get the memo.  June, July and August are the three warmest months of the year so statistically speaking, September marks the start of fall.  5 out of the first 8 days of the month have been above average and this week is starting off especially steamy with 90s today and tomorrow.  The longer range 8 to 14 day forecast from the Climate Prediction Center keeps the heat coming with Illinois and the rest of the midwest outlooked with a high probability of above average temperatures overall through the third week of the month (see image below).

We aren’t the only ones feeling the heat.  90s will surge northward on southerly winds into northeast Iowa, southern Minnesota and southwestern Wisconsin with heat index values at or above 100°.  Heat advisories have been issued for those areas today.





Tim's Weather World: Hoping for some September rain


Less than one inch of rain has fallen during the past four weeks at O’Hare.  August is typically the rainiest month but we saw a paltry 1.69″ of rain or 34% of average rainfall.  The prospects for significant rain aren’t very good over the next seven days.  We may see a few widely scattered showers or thunderstorms late Saturday.  We also have a chance for a few thunderstorms Tuesday night or early Wednesday but most of the 7 day forecast is calling for dry weather.  The longer range 8 to 14 day forecast from the Climate Prediction Center has most of the midwest outlooked for below average precipitation overall (see image below).




The latest update from the US Drought Monitor shows that portions of northern Illinois are “abnormally dry” while downstate the drought has deepened.  The area in moderate drought has nearly doubled to just under 40% compared to a week ago while just over 2% of the state is now in an extreme drought.








Tim's Weather World: Reflecting on a summer that was about average

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While there were ups and downs this meteorological summer (June through August), in the end the summer of 2013 was rather average.


The average temperature was 71.6° or .2° below average.  There have been 66 cooler summers than this past one and 75 warmer summers.


Rainfall totaled 10.14″ or 1.91″ less than the average of 12.05″.  There have been 66 drier summers and 76 wetter summers compared to 2013.


Some other items of note pertaining to this past summer:


  • There were just 9 90° days (days in which highs hit 90 or more), last summer there were 40
  • June had nearly 3″ more rainfall than normal but July was down more than an inch and August more than 3″ from average
  • 96° was the hottest high this summer occurring on July 9th and August 27th & 30th
  • 43° was the coolest low occurring on June 2nd and June 3rd
  • The longest streak of below average highs occurred between July 23rd and August 5th, 14 days in a row
  • The longest streak of at or above average highs was between August 20th and 31st with 12 days in a row




Tim's Weather World: A scorcher today, warm weekend and then feeling like fall

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There has been a remarkable reversal in the longer range outlook from the Climate Prediction Center for the start of December. Just a few days ago the forecast had most of the country, including the midwest, outlooked for overall above average temperatures (see top image below). The most recent forecast for roughly the same period now has the midwest and much of the northeast outlooked for cooler than average weather (see bottom image below).








First things first…


It will be a scorcher today with highs in the lower to middle 90s and heat index values approaching 100°.   A front will come through this evening with the hope for at least a few thunderstorms to bring some much needed rain to the area. This weekend might feel less like Labor Day weekend and more like July 4th weekend (at least Saturday and Sunday) with highs typical for July and ample humidity too. Then a stronger front comes crashing through late Sunday to usher in cooler Canadian air as our highs slip back into the 70s for Labor Day and Tuesday.




Tim's Weather World: Plainfield tornado anniversary

Plainfield tornado23 years ago today the most powerful August tornado to strike the United States ripped through the southwest suburbs.  The Plainfield tornado killed 29 people and injured over 350 others. 


The storm that spawned the tornado developed first in southern Wisconsin and then moved southeast across the state line towards Plainfield and Joliet.   Most tornados tend to move from the southwest to the northeast.  The movement of the storm wasn’t the only thing unusual about it though.  The Chicago office of the National Weather Service noted several things that made this tornado unique:


  • It was the first ever rated greater than F3 in August in the state of Illinois.
  • It was only the second killer tornado to occur in Illinois during the month of August.
  • Twenty-three years later it remains the only F5/EF5 tornado ever documented in the U.S. during the month of August. In fact, only 0.2% of all tornadoes in August have been rated F4/EF4 or greater.
  • The tornado was shrouded by low clouds and rain, making it difficult to see. As a result, no known photographs or videos of the tornado exist.

  • It is the only F5 tornado to strike in the US during the month of August.

Plainfield visibile imagery

It is the 15th most damaging tornado between 1890-1990 according to the National Severe Storms Laboratory ranking.  It left a damage path over 16 miles long that was as wide as 1/2 mile at times.  The visible satellite imagery (see above) from that day shows the storm growing rapidly that afternoon.





Tim's Weather World: Get set to sweat

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It appears summer will end steamy.  The worst of the heat will be today and tomorrow but temperatures should remain above average all the way through Labor Day weekend.   Our RPM model is indicating the combination of heat and humidity will make it feel like nearly 100° today and over 100° for most areas on Tuesday (see images below).   The National Weather service has more detailed information on how the heat index is derived along with the hazards associated with excessive heat.


Tomorrow’s high will be in the middle to upper 90s.  It will rival July 19th as the hottest day of the year.   O’Hare hit 96° on that date.  A “back door” cold front will bring in some relief Wednesday and Thursday turning winds off the lake but highs will still be about 5 to 10° above average.  The longer range 6 to 10 day and 8 to 14 day forecasts from the Climate Prediction Center outlooks us for above average temperatures overall through the first week of September.


DMA - Today Predicted Heat Index

DMA - Tomorrow Predicted Heat Index