A very broad and stacked ridge of subtropical high pressure built northward over most of the United States, bringing unseasonable heat and at times record high dewpoints to much of the Midwest.  Central Indiana's far western and southwestern counties, as well as central and northern portions of the Indianapolis Metro Area, recorded excessive heat (Heat Index values greater than 110 degrees) on August 20th-21st before a relatively mild day on August 22nd brought only 105-109 degree maximum Heat Index values to the region's southwestern-most zones.  August 23rd-25th then saw the region's most pronounced heat and humidity, with Excessive Heat criteria reached on the 23rd over western and northern counties, before the greatest expanse of Excessive Heat on the 24th which enveloped all but far-northeastern zones, with Excessive Heat continuing to persist through the 25th over most central and southern counties.
A cold frontal passage late on the 25th introduced milder conditions, but not before nearly all of the region had recorded at least three consecutive days with Heat Index values surpassing 105 degrees, with many locations observing at least one day with a Heat Index of 115 degrees or greater.  Greatest Heat Index values were reported along the lower Wabash Valley, including 122 degrees at Terre Haute on both the 24th and 25th, while a Heat Index of 118 degrees was recorded as far north and east as Kokomo (on the 24th).  Indianapolis' heat index officially peaked at 111 degrees on both the 24th and 25th.  Highest temperatures occurred on the 25th, including 102 degrees at the Shoals 8 S (Martin County) and 100 degrees at the Farmersburg TV-2 (Sullivan County) COOP sites.  Dewpoints amid Excessive Heat were most often in the upper 70s, although a broad swath of low 80s occurred along the entire Wabash Valley on the 23rd, before the Kokomo AWOS reported a dewpoint of 84 degrees on the 24th;  Indianapolis' highest dewpoint was meanwhile 81 degrees - reached briefly on both the 24th and 25th.
Daily minimum temperatures trended from the upper 60s to mid-70s on the 21st and 22nd, to several reports of upper 70s on the mornings of the 24th and 25th, including a low of 81 degrees at the Rockville (Parke County) COOP station.  Only two of the region's 39 counties (Henry and Randolph) did not reach Excessive Heat criteria, while two others (Brown and Delaware) only verified criteria for a few afternoon hours on a single day (the 24th).

Excessive Heat in BARTHOLOMEW, INDIANA
From 23-AUG-23 13:00:00 to 24-AUG-23 17:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 24th.  Heat index values were estimated from reported maximum temperatures at the Columbus COOP station and dewpoint data from the nearby GEZ ASOS.

Excessive Heat in BOONE, INDIANA
From 23-AUG-23 12:00:00 to 25-AUG-23 15:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 24th.  Heat index values were from measured temperature and dewpoint at the TYQ AWOS.

Excessive Heat in BROWN, INDIANA
From 24-AUG-23 15:00:00 to 24-AUG-23 16:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Criteria was reached from maximum heat index values exceeding 110 degrees briefly on the afternoon of August 24th.  Heat index values were estimated from measured temperature and dewpoint at the BMG ASOS, and reported maximum temperatures at the nearby Columbus and Oolitic COOP stations.

Excessive Heat in CARROLL, INDIANA
From 23-AUG-23 14:00:00 to 24-AUG-23 18:30:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 23rd.  Heat index values were from measured temperature and dewpoint at the MCX AWOS.

Excessive Heat in CLAY, INDIANA
From 21-AUG-23 12:00:00 to 24-AUG-23 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the early afternoon of August 21st over mainly western portions of Clay County.  Heat index values were estimated from measured temperature and dewpoint at the nearby HUF ASOS.

Excessive Heat in CLINTON, INDIANA
From 23-AUG-23 14:10:00 to 24-AUG-23 18:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 23rd over northern and central portions of Clinton County.  Heat index values were from measured temperature and dewpoint at the FKR AWOS.

Excessive Heat in DAVIESS, INDIANA
From 21-AUG-23 11:30:00 to 25-AUG-23 16:50:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the early afternoon of August 21st.  Heat index values were from measured temperature and dewpoint at the DCY AWOS.

Excessive Heat in DECATUR, INDIANA
From 23-AUG-23 13:00:00 to 25-AUG-23 17:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 24th.  Heat index values were estimated from measured temperature and dewpoint at the HLB AWOS.

Excessive Heat in DELAWARE, INDIANA
From 24-AUG-23 16:00:00 to 24-AUG-23 18:30:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Criteria was reached from maximum heat index values exceeding 110 degrees only on the afternoon of August 24th, over central and western portions of Delaware County.  Heat index values were from measured temperature and dewpoint at the MIE ASOS.

Excessive Heat in FOUNTAIN, INDIANA
From 23-AUG-23 13:00:00 to 25-AUG-23 16:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 23rd.  Heat index values were estimated from reported maximum temperature at the nearby Perrysville 4 WNW COOP station and dewpoint data at the LAF ASOS.

Excessive Heat in GREENE, INDIANA
From 21-AUG-23 12:00:00 to 25-AUG-23 18:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the early afternoon of August 21st over the western half of Greene County.  Heat index values were estimated from measured temperature and dewpoint at both the the BMG ASOS and RSV AWOS.

Excessive Heat in HAMILTON, INDIANA
From 20-AUG-23 13:55:00 to 25-AUG-23 16:55:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 20th over south-central portions of Hamilton County.  Heat index values were from measured temperature and dewpoint at the UMP AWOS.

Excessive Heat in HANCOCK, INDIANA
From 23-AUG-23 13:00:00 to 25-AUG-23 17:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 24th over most of Hancock County.  Heat index values were estimated and interpolated from measured temperature and dewpoint at the MQJ and UMP AWOS and reported maximum temperatures from the Greenfield COOP station.

Excessive Heat in HENDRICKS, INDIANA
From 23-AUG-23 14:00:00 to 25-AUG-23 17:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 24th.  Heat index values were estimated from proximity to nearby ASOS at both IND and EYE.

Excessive Heat in HOWARD, INDIANA
From 23-AUG-23 13:25:00 to 24-AUG-23 18:56:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 23rd over essentially all of Howard County.  Heat index values were from measured temperature and dewpoint at the OKK AWOS.

Excessive Heat in JACKSON, INDIANA
From 23-AUG-23 13:00:00 to 25-AUG-23 17:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 24th.  Heat index values were estimated from reported maximum temperatures at the Seymour 1 WSW COOP station and dewpoint data from the nearby BFR AWOS.

Excessive Heat in JENNINGS, INDIANA
From 23-AUG-23 13:00:00 to 25-AUG-23 17:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 24th over mainly western portions of Jennings County.  Heat index values were estimated and interpolated from reported maximum temperatures from the North Vernon 2 ESE COOP station and dewpoint data from the nearby HLB and IMS AWOS.

Excessive Heat in JOHNSON, INDIANA
From 23-AUG-23 13:00:00 to 25-AUG-23 18:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 24th over most of Johnson County.  Heat index values were from reported maximum temperature at the Franklin WWTP COOP station and dewpoint data from the IND and GEZ ASOS and the HFY AWOS.

Excessive Heat in KNOX, INDIANA
From 20-AUG-23 14:00:00 to 25-AUG-23 17:30:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Criteria was reached from maximum heat index values exceeding 110 degrees on the early afternoon of August 21st.  Heat index values are estimated from combination of observed maximum temperatures at the Vincennes 5 NE COOP station and estimated dewpoints from proximity to nearby LWV ASOS and DCY and AJG AWOS.

Excessive Heat in LAWRENCE, INDIANA
From 23-AUG-23 13:00:00 to 25-AUG-23 17:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 24th.  Heat index values were interpolate from data reported by the nearby Hardin Ridge RAWS station.

Excessive Heat in MADISON, INDIANA
From 23-AUG-23 13:00:00 to 25-AUG-23 16:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 23rd over far western portions of Madison County.  Heat index values were estiamted and interpolated from measured temperature and dewpoint at both the nearby UMP AWOS and MIE ASOS.

Excessive Heat in MARTIN, INDIANA
From 21-AUG-23 12:00:00 to 25-AUG-23 17:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 21st over the southwestern half of Martin County.  Heat index values were estimated from reported maximum temperature at the Shoals 8 S COOP station and dewpoint at the nearby DCY AWOS.

Excessive Heat in MONROE, INDIANA
From 23-AUG-23 13:00:00 to 25-AUG-23 18:45:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 24th.  Heat index values were from measured temperature and dewpoint at the BMG ASOS.

Excessive Heat in MONTGOMERY, INDIANA
From 23-AUG-23 13:00:00 to 25-AUG-23 16:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 23rd to the west and north of Crawfordsville.  Heat index values were estimated and interpolated given temperature and dewpoint data from the nearby LAF ASOS and reported maximum temperature from the Crawfordsville 6 SE COOP station.

Excessive Heat in MORGAN, INDIANA
From 23-AUG-23 13:00:00 to 25-AUG-23 18:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 24th.  Heat index values were estimated from reported maximum temperature at the Martinsville 2 SW COOP station and dewpoint data from the nearby IND ASOS.

Excessive Heat in OWEN, INDIANA
From 23-AUG-23 12:00:00 to 25-AUG-23 18:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 24th.  Heat index values were from estimated from reported maximum temperatures at the Spencer COOP station and dewpoint data from the nearby BMG ASOS.

Excessive Heat in PARKE, INDIANA
From 21-AUG-23 12:00:00 to 25-AUG-23 16:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Criteria was reached from maximum heat index values exceeding 110 degrees on the early afternoon of August 21st over mainly central and southwestern portions of Parke County.  Heat index values were estimated from reported maximum temperature at the Rockville COOP station and dewpoint at the nearby HUF ASOS.

Excessive Heat in PUTNAM, INDIANA
From 23-AUG-23 12:00:00 to 25-AUG-23 16:35:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 24th.  Heat index values were from measured temperature and dewpoint at the GPC AWOS.

Excessive Heat in RUSH, INDIANA
From 24-AUG-23 16:00:00 to 24-AUG-23 18:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Criteria was reached from maximum heat index values exceeding 110 degrees briefly on the afternoon of August 24th.  Heat index values were estimated from reported maximum temperature at the Rushville COOP station and dewpoint data from the GEZ ASOS and HLB AWOS.

Excessive Heat in SHELBY, INDIANA
From 23-AUG-23 13:00:00 to 25-AUG-23 18:05:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 24th.  Heat index values were from measured temperature and dewpoint at the GEZ ASOS as well as maximum temperatures from the Shelbyville COOP station.

Excessive Heat in SULLIVAN, INDIANA
From 21-AUG-23 11:00:00 to 25-AUG-23 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Criteria was reached from maximum heat index values exceeding 110 degrees on the early afternoon of August 21st for essentially all of Sullivan County.  Heat index values were estimated from reported maximum temperature at Farmersburg TV-2 COOP station and dewpoint data from the RSV AWOS.

Excessive Heat in TIPPECANOE, INDIANA
From 23-AUG-23 13:45:00 to 24-AUG-23 18:50:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 23rd.  Heat index values were from measured temperature and dewpoint at the LAF ASOS.

Excessive Heat in TIPTON, INDIANA
From 23-AUG-23 13:00:00 to 25-AUG-23 16:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 23rd.  Heat index values were estimated from reported maximum temperature from the Tipton 5 SW COOP station and dewpoint data from the OKK AWOS.

Excessive Heat in VERMILLION, INDIANA
From 21-AUG-23 12:00:00 to 25-AUG-23 16:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the early afternoon of August 21st.  Heat index values were estimated from measured temperature and dewpoint at the nearby HUF ASOS and DNV AWOS.

Excessive Heat in VIGO, INDIANA
From 21-AUG-23 11:25:00 to 25-AUG-23 19:20:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the early afternoon of August 21st for essentially all of Vigo County.  Heat index values were from measured temperature and dewpoint at the HUF ASOS.

Excessive Heat in WARREN, INDIANA
From 23-AUG-23 14:00:00 to 24-AUG-23 18:30:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 23rd.  Heat index values were estimated from measured temperature and dewpoint at both the LAF ASOS and DNV AWOS.

Excessive Heat in MARION, INDIANA
From 20-AUG-23 13:55:00 to 25-AUG-23 15:05:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Criteria was reached from maximum heat index values exceeding 110 degrees on the afternoon of August 20th within downtown and northeastern portions of Marion County.  Heat index values were from measured temperature and dewpoint at both the IND and EYE ASOS and nearby UMP AWOS.