Near Normal Temperatures, but a Heatwave Still Blazes in August

September 12, 2023 // Article by: Shawn McGarrity


A drier weather pattern made a return to the Chicagoland area this August, with the month’s rainfall total of 1.33” falling well short of the 4.25” typically seen. Temperatures, on the other hand, exceeded the norm, with the average for the month being 74.3­°F (0.5°F warmer than normal).

The month started off dry and warm across the region as daytime highs trended upward from the mid 80s up to the low 90s by the 3rd. The first bit of rain arrived on the 5th in the form of some showers and storms, after which temperatures cooled back to the 70s in subsequent days. 

The second week of August featured a return to more seasonable temperatures and quieter weather. A weak disturbance on the 11th brought some showers to the west of the city, however most activity fell apart as it pushed east, leaving the immediate area dry. A more formidable system on the 14th brought the best rainfall of the month, with 0.80” of rain being reported at O’Hare (making up over half of the month’s rainfall total) and locally higher in downpours. Temperatures cooled during this unsettled period that lasted through the 17th, with daytime highs struggling to get out of the 70s.

The remainder of the month saw a persistent dry trend across the area as temperatures warmed. Highs topped the 90°F mark on the 20th with this heat wave lingering for several days thereafter. This heat wave was associated with a moist airmass which made the already uncomfortable heat feel even hotter. Dew points at O’Hare topped 80°F on the 23rd, the first time since July 30, 1999. The heat wave peaked on the 24th with temperatures reaching 100°F (the hottest of the month), the first triple-digit day since July 6, 2012 and tying the day’s record high set in 1947. Coupled with the excessive humidity, heat indices reached 120°F, breaking the all-time record high heat index set on July 13, 1995 at 118°F.

A disturbance producing storms missed the area to the north on the 24th, but behind it brought relief from the unbearable heat. Highs then fell to the low 80s and bottomed out in the 70s through the end of the month.


August fared near average in regard to temperatures, with the overall average temperature of 74.5°F falling only 0.2°F cooler than normal. Unlike other areas in the Midwest which saw far departures in monthly rainfall, Indianapolis ended up rather close, with 2.97” of the normal 3.20” reported. 

A drier pattern started off the month as high temperatures held in the mid to upper 80s. The first batch of rainfall returned on the 5th with showers and storms returning in subsequent days. A more organized system on the 9th brought the month’s best rainfall, with 0.98” reported in the city. A west-east corridor of heavier rainfall occurred to the north of the city, producing 1.5” - 3” of rain in spots. 

A brief break from the unsettled weather returned for the 10th and 11th before scattered showers and storms–some of which were severe–returned on the 12th. More widespread showers worked through the region on the 14th, bringing about three-quarters of an inch of additional rainfall. Temperatures cooled during this unsettled period, with highs only reaching the 70s. 

Other than passing storms on the 17th, the rest of August saw a dry, albeit hotter, pattern take hold. Daytime temperatures exceeded 90°F from the 20th to the 25th, peaking at 94°F on the 24th with heat indices reaching 111°F at Indianapolis International Airport. Cooler temperatures returned starting the 26th as highs fell with each subsequent day, cooling to the 70s by the 30th and 31st.

Peak heat indices across Central Indiana on August 24th. Couresty of NWS Indianapolis.


Overall, temperatures across the area were a bit cooler than normal. Columbus and Cincinnati had average temperatures of 73°F and 74.5°F (1°F and 0.4°F below normal, respectively). Rainfall, however, varied considerably between the two cities. Whereas Columbus saw abundant rainfall (with their 4.48” far exceeding the typical 3.74”), Cincinnati ended the month drier with only 1.85” of the typical 3.43”.

Quieter conditions were around to start off the month in both cities as highs were in the 80s. Other than a few stray showers in the Columbus area on the 4th and 6th, the region held dry through the first week of August. 

A cluster of storms moved through Cincinnati on the 7th, bringing better rainfall to the area and largely missing Columbus in the process. A few returning rounds of showers and storms occurred throughout the week that followed, with activity the 9th, 12th and 14th all favoring the Columbus area, with the last of these storms bringing nearly an inch to the capital. Cooler temperatures accompanied the unsettled weather of the 14th and 15th, with highs only reaching the 70s. 

After a final round of showers and storms on the 17th (which, in this case, favored Cincinnati), a drier trend developed that carried through to the 24th. During this time, temperatures trended warmer. Columbus saw their hottest day on the 21st with a high of 92°F and Cincinnati reached 94°F both the 21st and 25th. While Columbus saw breaks from the heat during this time (with highs returning to the 80s on occasion), Cincinnati persisted with highs in excess of 90°F for five days.

Satellite image shows river valley fog and some overland fog across the Ohio Valley this morning. Fog visible (light blue) in river valleys across southern Ohio and Kentucky the morning of August 17th. Courtesy of NWS Wilmington. 

Showers and storms on the 24th brought a break from the heat for most areas and also provided the best rainfall for the month, with Columbus and Cincinnati reporting 2.44” and 0.71” of rain, respectively. Unsettled weather lingered around through the 26th, helping cool daytime highs to the low 80s. Quieter weather returned to close out the month, with highs cooling once more to the 70s across the region.