An Active Start and End to September 2021

Chicago Area:

September started rather quiet for much of the Midwest and the weather stayed relatively dry for the first week of the month.  And while there were a few showers around for the beginning of the Labor Day weekend, that Sunday and Labor Day itself offered plenty of sunshine with afternoon highs in the low 80s.

However, that quickly changed on the 7th as severe thunderstorms raked across northern Illinois as a cold front aproached the area.  The storms produced quarter to golf ball sized hail along with wind gusts of 60 - 80 mph! There was even a confirmed tornado near Joliet.  Here is a recap of the event from the National Weather Service in Chicago.

The cold front then swept across the area the night of the 7th followed by a large area of high pressure.  This resulted in a pleasant stretch of weather that lasted through September 10th and featured plenty of sunshine along with temperatures peaking in the mid to upper 70s.

Mid-summer warmth then returned for the next few days as afternoon highs pushed towards 90° and it was rather humid as well. There were a few showers and storms around during the afternoon hours, but nothing was severe.  Another cold front then made its way through the area early on the 15th and sent temperatures back to where they should be for mid-September.

The wash/rinse/repeat cycle really continued for the second half of the month.  A few dry, seasonable days would be followed by a warmer day or two along with scattered showers/storms until the next cold front arrived.  This type of pattern is very common for the month of September as the frequency of cold fronts increases and we turn the page to autumn.  

And despite the change of seasons, there was a record high temperature set in Rockford on September 27th as the thermometer reached 90°.  This broke the old record of 89° set back in 1954.  Elsewhere across northern Illinois, temperatures remained above normal for the last few days of the month, but it did stay rain free.

Here is a recap the almanac data for the month of September in Chicago (O'Hare International is official recording station).  The average temperature for the month was 70.3°...almost 4° above normal.  The highest temperature for September was 89° and this occurred on both the 17th and 19th.  The coolest temp occurred on the 25th of the month as the thermometer dipped to 50°.  Total precipitation was only 1.23", just about 2 inches below normal.

Central Indiana into Ohio:

The weather was relatively quiet to start off the month along the I-70 corridor, but that wasn't the case east of Columbus as the remnants of Ida produced heavy rain for the eastern third of the state.  A cold front that pushed across the Midwest early on September 1st is the main reason it stayed dry, eventually pushing Ida off the East Coast on the 2nd.  

Scattered showers and storms made their way through the region the night of the 7th as another cold front swept towards the Ohio Valley.  This was followed by a large area of high pressure that kept it rain free through September 13th.  However, temperatures and the humidity was on the rise after the 10th as afternoon highs pushed into the upper 80s to low 90s.  This would result in a few rounds of scattered showers and storms between the 14th and 15th of the month.

It then remained seasonably warm with just some afternoon "pop-up" storms between the 16th and 19th of September.  But, the next cold front was a slow mover and "set the stage" for areas of heavy rainfall between the 21st and 22nd.  Training storms and downpours resulted in flooding issues along the I-70 corridor.  Indianapolis received 2 - 3 inches of rain with this event while Dayton got just over 2 inches, much of this falling in a 12 hour period.  Then, as the front passed, temperatures took a tumble and by the afternoon of the 22nd, most locations were only in the upper 50s to low 60s.

The rest of the month was rather quiet with mainly dry, seasonable weather as a parade of cold fronts made their way across the region.  And again, as mentioned before, this is quite common for the end of September as we transition into early fall.