August 23-24, 2023: Late Summer Heat Wave Results in Consecutive Days With 115°+ Heat Indices

Storm Reports

The heat of August 23-24 in perspective...

Overview
August 23
August 24
Dew Points and How the Air Feels
Links

Overview

An expansive ridge of high pressure over the central United States brought several days of record-breaking temperatures to this part of the country during the 4th week of August.

In northern Illinois and northwest Indiana, a brief spurt of heat and humidity occurred on Sunday, August 20th before a cold front brought some relief to the area on Monday and Tuesday.

The worst of the heat and humidity, however, arrived on Wednesday, August 23rd and continued into Thursday, August 24th.

Chicago officially observed a high temperature of 98°F on the 23rd at O'Hare Airport, setting a new record daily high temperature for this date. The peak heat index observed at O'Hare Airport on the 23rd was 116°F**.

Chicago officially observed a high temperature of 100°F on the 24th at O'Hare Airport, tying the record daily high temperature for this date. The peak heat index observed at O'Hare Airport on the 24th was 120°F**.

Chicago logged two days in a row with peak heat indices greater than 115°F, which was the first time that this occurred since the deadly heat wave of July 1995.

Rockford officially observed a high temperature of 97°F and also recorded a peak heat index of 118°F on both the 23rd and 24th.

** These heat index readings were from intra-hour observations. See the August 24 tab for an explanation on an important caveat about this.

Map showing all of the National Weather Service Watches, Warnings, and Advisories that were in effect the afternoon of Wednesday, August 23rd. The magenta color across much of the central part of the country shows where the Excessive Heat Warnings were in effect on this date.

August 23

Chicago:

Chicago officially observed a high temperature of 98°F at O'Hare Airport. This broke Chicago's previous daily record high temperature for August 23rd of 97°F that was set back in 1947.

Chicago also observed a low temperature of 77°F at O'Hare Airport. This broke Chicago's previous daily record high minimum temperature for August 23rd of 76°F that was set back in 1968.

Chicago's peak observed heat index for the day was 116°F**, one of the highest heat indices ever observed in Chicago.

Chicago-O'Hare's highest observed dew point temperature over the course of the day was 80°F. This was the first time that the dew point reached 80°F in Chicago since July 30, 1999, and made August 23rd only the 7th calendar day on record where a dew point of 80°F or greater was observed in Chicago (the highest recorded dew point in Chicago's history was 83°F on July 30, 1999).

** This heat index reading was from an intra-hour observation. See the August 24 tab for an explanation on an important caveat about this.

Rockford:

Rockford officially observed a high temperature of 97°F at Rockford Airport, falling shy of the record high temperature for August 23rd of 101°F that was set back in 1947.

Rockford's peak observed heat index for the day was 118°F, one of the highest heat indices ever observed in Rockford. The highest heat index ever recorded at Rockford's official climate observation site is 125°F, which was observed on July 13, 1995.

Listing of High Temperatures and Peak Heat Indices Across the Area:

Public Information Statement
National Weather Service Chicago IL
759 PM CDT Wed Aug 23 2023

...HIGH TEMPERATURES AND PEAK HEAT INDICES FROM 8/23/2023...

Below is a listing of high temperatures and peak heat indices
observed on Wednesday, August 23rd at ASOS and AWOS sites across
the NWS Chicago forecast area.


...HIGH TEMPERATURES...

Location                      Temp     Provider
Wheeling - Chicago Exec. Arp  99 F     ASOS
Waukegan Airport              98 F     ASOS
Chicago - OHare               98 F     ASOS
Chicago - Midway              98 F     ASOS
Rockford Airport              97 F     ASOS
Gary Airport                  97 F     AWOS
Joliet Airport                97 F     AWOS
Dixon Airport                 97 F     AWOS
Schaumburg Airport            96 F     AWOS
West Chicago - DuPage Arpt.   95 F     ASOS
Morris Airport                95 F     AWOS
Lansing Airport               95 F     AWOS
Romeoville - NWS Chicago      94 F     Official NWS Observation
Sugar Grove - Aurora Arpt.    94 F     ASOS
Rochelle Airport              94 F     AWOS
Pontiac Airport               94 F     AWOS
Peru Airport                  94 F     AWOS
Kankakee Airport              94 F     AWOS
DeKalb Airport                94 F     AWOS
Valparaiso Airport            93 F     ASOS
Rensselaer Airport            90 F     AWOS


...PEAK HEAT INDICES...

Location                     Heat Idx.  Provider
Morris Airport               124 F      AWOS
Dixon Airport                121 F      AWOS
Joliet Airport               119 F      AWOS
Rockford Airport             118 F      ASOS
Sugar Grove - Aurora Arpt.   117 F      ASOS
Peru Airport                 117 F      AWOS
Waukegan Airport             116 F      ASOS
Chicago - OHare              116 F      ASOS
Chicago - Midway             116 F      ASOS
Wheeling - Chicago Exec. Arp 116 F      ASOS
Pontiac Airport              116 F      AWOS
West Chicago - DuPage Arpt.  115 F      ASOS
Kankakee Airport             115 F      AWOS
Schaumburg Airport           114 F      AWOS
Rochelle Airport             113 F      AWOS
Valparaiso Airport           112 F      ASOS
DeKalb Airport               112 F      AWOS
Rensselaer Airport           109 F      AWOS

Observations are collected from a variety of sources with varying
equipment and exposures. We thank all volunteer weather observers
for their dedication. Not all data listed are considered official.

$$

August 24

Chicago:

Chicago officially observed a high temperature of 100°F at O'Hare Airport. This tied Chicago's daily record high temperature for August 24th that was set back in 1947.
- This was Chicago's first recorded 100°F temperature since July 6, 2012.
- This also tied for the fifth latest 100°F observation (in a calendar year) to occur in Chicago.

Chicago's peak observed heat index for the day was 120°F**, which is the highest heat index ever recorded at Chicago's official climate observation site.
- ** Important caveat: This heat index reading was from an intra-hour observation. Intra-hour observations only date back to 1996. Heat indices prior to 1996 were reported once per hour and may not have accounted for higher high indices observed between hourly observations. Thus, it is possible there could have been intra-hour heat indices in the past, and especially on the day of the previous record, that reached or exceeded 120 degrees but were not recorded.
- The highest heat index reported in an hourly observation both on this date and on the day of the previous record (July 13, 1995) was 118°F.

Rockford:

Rockford once again officially observed a high temperature of 97°F at Rockford Airport, falling shy of the record high temperature for August 24th of 102°F that was set back in 1947.

Rockford observed a low temperature of 78°F at Rockford Airport. This broke Rockford's previous daily record high minimum temperature for August 24th of 74°F that was set back in 1947.

Rockford's peak observed heat index for the day was also once again 118°F, one of the highest heat indices ever observed in Rockford. The highest heat index ever recorded at Rockford's official climate observation site is 125°F, which was observed on July 13, 1995.

Listing of High Temperatures and Peak Heat Indices Across the Area:

...HIGH TEMPERATURES AND PEAK HEAT INDICES FROM 8/24/2023...

Below is a listing of high temperatures and peak heat indices
observed on Thursday, August 24th at ASOS and AWOS sites across
the NWS Chicago forecast area.


...HIGH TEMPERATURES...

Location                     Temp       Provider
Waukegan Airport             100 F      ASOS
Chicago - OHare              100 F      ASOS
Wheeling - Chicago Exec. Arp 100 F      ASOS
Chicago - Midway             100 F      ASOS
Joliet Airport                98 F      AWOS
Schaumburg Airport            98 F      AWOS
Rockford Airport              97 F      ASOS
West Chicago - DuPage Arpt.   97 F      ASOS
Gary Airport                  97 F      AWOS
Romeoville - NWS Chicago      96 F      Official NWS Observation
Valparaiso Airport            96 F      ASOS
Sugar Grove - Aurora Arpt.    96 F      ASOS
Pontiac Airport               96 F      AWOS
Lansing Airport               96 F      AWOS
Dixon Airport                 95 F      AWOS
Peru Airport                  95 F      AWOS
Kankakee Airport              95 F      AWOS
Morris Airport                95 F      AWOS
DeKalb Airport                94 F      AWOS
Rochelle Airport              93 F      AWOS
Rensselaer Airport            91 F      AWOS


...PEAK HEAT INDICES...

Location                     Heat Idx.  Provider
Chicago - OHare              120 F      ASOS
Waukegan Airport             120 F      ASOS
Morris Airport               119 F      AWOS
Chicago - Midway             118 F      ASOS
Rockford Airport             118 F      ASOS
Joliet Airport               117 F      AWOS
Dixon Airport                117 F      AWOS
Wheeling - Chicago Exec. Arp 117 F      ASOS
Pontiac Airport              116 F      AWOS
Sugar Grove - Aurora Arpt.   116 F      ASOS
Peru Airport                 115 F      AWOS
Kankakee Airport             115 F      AWOS
Valparaiso Airport           115 F      ASOS
West Chicago - DuPage Arpt.  114 F      ASOS
Schaumburg Airport           114 F      AWOS
Rensselaer Airport           113 F      AWOS
Rochelle Airport             109 F      AWOS
DeKalb Airport               109 F      AWOS

Observations are collected from a variety of sources with varying
equipment and exposures. We thank all volunteer weather observers
for their dedication. Not all data listed are considered official.

$$

Dew Points are Often a Better Indicator than Humidity for How the Air Feels!

The hot and humid air mass that blanketed the area on Wednesday and Thursday is on the high end of oppressive humidity that we can experience in the summer. Did you know that the dew point temperature is a better way to quantify how the air feels in the summer? In the inset chart scaling dew point temperatures to how the air feels, you can see that oppressive-feeling dew points start around 75°, so the widespread upper 70s to lower 80s dew points (and locally mid 80s near farm fields) that occurred on Wednesday and Thursday are well into the “oppressive” range. With air temperatures well into the 90s to around 100°, dew points this high directly contribute to the greatly increased risk of heat-related illnesses posed by the extreme heat.

Links

Recent Records Across the Country

Local Climate Page (including climate records)

NWS Chicago Science and Past Events Page

Storm Impacting the Northwest U.S.; Fire Weather Conditions in Southern California; Severe Weather in the South

August 23-24, 2023: Late Summer Heat Wave Results in Consecutive Days With 115°+ Heat Indices