Late Summer 2023 Heat Wave Recap

Overview

A very large and strong upper level ridge of high pressure over the central United States brought several days of record temperatures during the 4th week of August. Temperatures in the upper 90s to low 100s were observed each day across eastern IA, northwest IL, and northeast MO. These readings combined with dewpoints in the 70s and even low 80s resulted in heat indices over 100 degrees for several hours each day.

Several cooling centers were opened during the week and many schools adjusted their schedules and extra-curricular activities to keep kids safe in the heat. Some heat-related illnesses were also reported during the week.

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.

Temperature
Dewpoint / Heat Index
Environment
Additional

Temperature


Figure 1: Temperature Facts	Figure 2: Moline IL Record High

Dewpoint / Heat Index


Figure 1: Dewpoint Facts	Figure 2: Moline, IL Heat Index Climatology	Figure 3: Dubuque, IA Heat Index Climatology	Figure 4: Moline, IL Heat Index Probability

Sunday 08/20 Highest Heat Indices	Tuesday 08/22 Highest Heat Indices
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. Location Heat Index Time/Date Provider Keokuk Arpt 113 F 0315 PM 08/20 AWOS Marion 113 F 0315 PM 08/20 CWOP Olin 113 F 0410 PM 08/20 CWOP Freeport Arpt 113 F 0415 PM 08/20 AWOS Eldridge 113 F 0515 PM 08/20 CWOP Dubuque 112 F 0236 PM 08/20 CWOP Dubuque 112 F 0258 PM 08/20 CWOP Macomb 112 F 0330 PM 08/20 CWOP Sigourney 112 F 0340 PM 08/20 MESOWEST University Heights 112 F 0340 PM 08/20 MESOWEST Sterling/Rock Falls Arpt 112 F 0356 PM 08/20 AWOS De Witt 112 F 0455 PM 08/20 MESOWEST Iowa City 112 F 0617 PM 08/20 CWOP Cedar River Tnc Swamp 111 F 1246 PM 08/20 RAWS Milan 111 F 0228 PM 08/20 CWOP Independence 111 F 0300 PM 08/20 CWOP 1.4 S Hills 111 F 0320 PM 08/20 MESOWEST Independence 111 F 0330 PM 08/20 CWOP Robins 111 F 0411 PM 08/20 CWOP Macomb 111 F 0427 PM 08/20 CWOP Stronghurst 111 F 0439 PM 08/20 CWOP Shimek State Forest 111 F 0507 PM 08/20 RAWS Fort Madison Arpt 111 F 0535 PM 08/20 AWOS Iowa City I-80 111 F 0545 PM 08/20 MESOWEST Iowa City 110 F 0139 PM 08/20 CWOP Dubuque 110 F 0225 PM 08/20 MESOWEST Victor 110 F 0420 PM 08/20 MESOWEST 3 S Mount Joy 110 F 0445 PM 08/20 AWS Williamsburg 110 F 0550 PM 08/20 MESOWEST Muscatine Arpt 109 F 1235 PM 08/20 AWOS Monmouth 109 F 0235 PM 08/20 CWOP Monmouth 109 F 0315 PM 08/20 ISWS Aurora 109 F 0315 PM 08/20 CWOP Davenport Arpt 109 F 0352 PM 08/20 ASOS Riverside 109 F 0428 PM 08/20 CWOP Tipton 109 F 0440 PM 08/20 CWOP Tipton 109 F 0500 PM 08/20 MESOWEST Stockton 108 F 0245 PM 08/20 CWOP Burlington Arpt 108 F 0253 PM 08/20 ASOS New London 108 F 0350 PM 08/20 CWOP Fairfield Arpt 108 F 0415 PM 08/20 AWOS Iowa City 108 F 0443 PM 08/20 CWOP Flagstaff Cheshire 108 F 0445 PM 08/20 CWOP Clinton Arpt 108 F 0556 PM 08/20 AWOS Fairbank 107 F 0230 PM 08/20 CWOP Quad Cities 107 F 0435 PM 08/20 MESOWEST Urbana 107 F 0445 PM 08/20 CWOP Savanna Arpt 107 F 0523 PM 08/20 AWOS Big Bend 107 F 0525 PM 08/20 ISWS Iowa City 107 F 0557 PM 08/20 CWOP Davenport 107 F 0600 PM 08/20 CWOP Winthrop 106 F 0300 PM 08/20 CWOP Cedar Rapids Arpt 106 F 0352 PM 08/20 ASOS Dubuque Arpt 106 F 0353 PM 08/20 ASOS Anamosa 106 F 0430 PM 08/20 MESOWEST Mount Pleasant Arpt 106 F 0455 PM 08/20 AWOS Iowa City Arpt 106 F 0552 PM 08/20 ASOS Muscatine 105 F 0415 PM 08/20 CWOP Maquoketa 105 F 0435 PM 08/20 MESOWEST Quad City Intl Arpt 105 F 0452 PM 08/20 ASOS Cedar Rapids I-380 105 F 0500 PM 08/20 MESOWEST Manchester 104 F 0150 PM 08/20 MESOWEST Freeport 104 F 0325 PM 08/20 ISWS Independence Arpt 103 F 0235 PM 08/20 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. Location Heat Index Time/Date Provider Macomb 116 F 0445 PM 08/22 CWOP Keokuk Arpt 116 F 0435 PM 08/22 AWOS Cantril 116 F 0500 PM 08/22 MESOWEST New London 115 F 0620 PM 08/22 CWOP Stronghurst 115 F 0432 PM 08/22 CWOP Independence 115 F 0400 PM 08/22 CWOP Aurora 115 F 0500 PM 08/22 CWOP Marion 114 F 0500 PM 08/22 CWOP Iowa City 114 F 0658 PM 08/22 CWOP Dubuque 114 F 0527 PM 08/22 CWOP Iowa City 114 F 0419 PM 08/22 CWOP Mount Pleasant 114 F 0500 PM 08/22 MESOWEST Freeport 113 F 0558 PM 08/22 CWOP Shimek State Forest 113 F 0307 PM 08/22 RAWS Fort Madison Arpt 113 F 0535 PM 08/22 AWOS Sigourney 113 F 0500 PM 08/22 MESOWEST Muscatine Arpt 112 F 0735 PM 08/22 AWOS Urbana 112 F 0500 PM 08/22 MESOWEST 1.4 S Hills 111 F 0650 PM 08/22 MESOWEST Winthrop 111 F 0345 PM 08/22 CWOP Cedar Rapids 111 F 0430 PM 08/22 CWOP Buffalo 111 F 0403 PM 08/22 CWOP Riverside 111 F 0525 PM 08/22 CWOP Dubuque 111 F 0500 PM 08/22 MESOWEST Iowa City I-80 111 F 0500 PM 08/22 MESOWEST Urbana 110 F 0500 PM 08/22 CWOP Iowa City 110 F 0538 PM 08/22 CWOP Mt. Carroll 110 F 0551 PM 08/22 CWOP Iowa City 110 F 0548 PM 08/22 CWOP Tipton 110 F 0500 PM 08/22 MESOWEST Williamsburg 110 F 0500 PM 08/22 MESOWEST University Heights 109 F 0640 PM 08/22 MESOWEST Olin 109 F 0425 PM 08/22 CWOP Tipton 109 F 0530 PM 08/22 CWOP Monmouth 109 F 0535 PM 08/22 ISWS Iowa City Arpt 109 F 0552 PM 08/22 ASOS 3 S Mount Joy 108 F 0535 PM 08/22 AWS Milan 108 F 0508 PM 08/22 CWOP Marion 108 F 0515 PM 08/22 CWOP Mount Carroll 108 F 0300 PM 08/22 CWOP Eldridge 108 F 0446 PM 08/22 CWOP Robins 108 F 0555 PM 08/22 CWOP Burlington Arpt 108 F 0553 PM 08/22 ASOS Cedar Rapids Arpt 108 F 0452 PM 08/22 ASOS Independence Arpt 108 F 0455 PM 08/22 AWOS Mount Pleasant Arpt 108 F 0415 PM 08/22 AWOS Sterling 107 F 0449 PM 08/22 CWOP Dubuque 107 F 0626 PM 08/22 CWOP Fairfield Arpt 107 F 0455 PM 08/22 AWOS Victor 107 F 0500 PM 08/22 MESOWEST Lone Tree 106 F 0420 PM 08/22 MESOWEST Middleburg 106 F 0615 PM 08/22 CWOP Dubuque 106 F 0619 PM 08/22 CWOP Monmouth 106 F 0535 PM 08/22 CWOP Clinton Arpt 105 F 0556 PM 08/22 AWOS Davenport Arpt 105 F 0452 PM 08/22 ASOS Anamosa 105 F 0500 PM 08/22 MESOWEST Manchester 105 F 0500 PM 08/22 MESOWEST Davenport 104 F 0645 PM 08/22 CWOP Big Bend 103 F 0635 PM 08/22 ISWS Sterling/Rock Falls Arpt 103 F 0456 PM 08/22 AWOS Spring Valley Airport 103 F 0435 PM 08/22 AWS Quad City Intl Arpt 102 F 0552 PM 08/22 ASOS Cedar Rapids I-380 102 F 0505 PM 08/22 MESOWEST Quad Cities 101 F 0500 PM 08/22 MESOWEST Muscatine 100 F 0500 PM 08/22 CWOP Savanna Arpt 100 F 0615 PM 08/22 AWOS Maquoketa 100 F 0500 PM 08/22 MESOWEST

Wednesday 08/23 Highest Heat Indices	Thursday 08/24 Highest Heat Indices
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. Location Heat Index Time/Date Provider Kahoka 124 F 0229 PM 08/23 CWOP ROBINS 124 F 0302 PM 08/23 CWOP Muscatine Arpt 124 F 0635 PM 08/23 AWOS University Heights 123 F 0450 PM 08/23 MESOWEST Flagstaff Cheshire 123 F 0430 PM 08/23 CWOP Urbana 123 F 0400 PM 08/23 CWOP Davenport 123 F 0415 PM 08/23 CWOP Stockton 123 F 0425 PM 08/23 CWOP Eldridge 123 F 0456 PM 08/23 CWOP Macomb 123 F 0219 PM 08/23 CWOP Clinton Arpt 123 F 0356 PM 08/23 AWOS Savanna Arpt 123 F 0438 PM 08/23 AWOS Sterling/Rock Falls Arpt 123 F 0156 PM 08/23 AWOS Stronghurst 122 F 0242 PM 08/23 CWOP Macomb 122 F 0315 PM 08/23 CWOP Big Bend 122 F 0335 PM 08/23 ISWS 3 S Mount Joy 121 F 0435 PM 08/23 AWS 3 NW Nauvoo 121 F 0250 PM 08/23 AWS New London 120 F 0420 PM 08/23 CWOP Shimek State Forest 120 F 0407 PM 08/23 RAWS Freeport 120 F 0235 PM 08/23 ISWS Monmouth 120 F 0235 PM 08/23 ISWS Iowa City Arpt 120 F 0452 PM 08/23 ASOS Iowa City 119 F 0448 PM 08/23 CWOP Dubuque Arpt 119 F 0353 PM 08/23 ASOS Davenport Arpt 119 F 1152 AM 08/23 ASOS Freeport Arpt 119 F 0215 PM 08/23 AWOS Lone Tree 118 F 0320 PM 08/23 MESOWEST Cedar Rapids Arpt 118 F 0352 PM 08/23 ASOS Monmouth 117 F 0205 PM 08/23 CWOP Cedar Rapids 117 F 0545 PM 08/23 CWOP Quad City Intl Arpt 117 F 0552 PM 08/23 ASOS Spring Valley Airport 117 F 0245 PM 08/23 AWS Keokuk Arpt 116 F 0315 PM 08/23 AWOS Fort Madison Arpt 116 F 0315 PM 08/23 AWOS Independence Arpt 116 F 0135 PM 08/23 AWOS Dubuque 115 F 0317 PM 08/23 CWOP Fairfield Arpt 115 F 0335 PM 08/23 AWOS Burlington Arpt 114 F 0410 PM 08/23 ASOS Muscatine 113 F 0445 PM 08/23 CWOP Mount Pleasant Arpt 113 F 0455 PM 08/23 AWOS Dubuque 112 F 0318 PM 08/23 CWOP 3 NNE Keswick 111 F 0405 PM 08/23 AWS Dubuque 110 F 0518 PM 08/23 CWOP	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. Location Heat Index Time/Date Provider 2.5 S Coralville 120 F 0310 PM 08/24 MESOWEST Dubuque 120 F 0515 PM 08/24 MESOWEST Middleburg 119 F 0515 PM 08/24 CWOP Olin 119 F 0335 PM 08/24 CWOP 3 NW Nauvoo 119 F 0533 PM 08/24 AWS Shimek State Forest 119 F 0407 PM 08/24 RAWS Independence 119 F 0601 PM 08/24 CWOP Monmouth 119 F 0355 PM 08/24 ISWS Sigourney 119 F 0615 PM 08/24 MESOWEST Urbana 118 F 0415 PM 08/24 CWOP New London 118 F 0550 PM 08/24 CWOP Aurora 118 F 0330 PM 08/24 CWOP Macomb 118 F 0345 PM 08/24 CWOP Monmouth 118 F 0455 PM 08/24 CWOP 1.4 S Hills 117 F 0330 PM 08/24 MESOWEST Davenport 117 F 0500 PM 08/24 CWOP Tipton 117 F 0550 PM 08/24 CWOP Winthrop 117 F 0315 PM 08/24 CWOP Keokuk Arpt 117 F 0535 PM 08/24 AWOS Fort Madison Arpt 117 F 0535 PM 08/24 AWOS Sterling/Rock Falls Arpt 117 F 0456 PM 08/24 AWOS Williamsburg 117 F 0140 PM 08/24 MESOWEST Flagstaff Cheshire 116 F 0430 PM 08/24 CWOP Macomb 116 F 0305 PM 08/24 CWOP Big Bend 116 F 0225 PM 08/24 ISWS Freeport 116 F 0445 PM 08/24 ISWS Davenport Arpt 116 F 0352 PM 08/24 ASOS Muscatine Arpt 116 F 0455 PM 08/24 AWOS De Witt 116 F 0525 PM 08/24 MESOWEST Tipton 116 F 0340 PM 08/24 MESOWEST Washington 116 F 0455 PM 08/24 AWS Iowa City 115 F 0618 PM 08/24 CWOP Cedar Rapids 115 F 0620 PM 08/24 CWOP Eldridge 115 F 0226 PM 08/24 CWOP Robins 115 F 0548 PM 08/24 CWOP Iowa City 115 F 0329 PM 08/24 CWOP Urbana 115 F 0710 PM 08/24 MESOWEST Marion 114 F 0545 PM 08/24 CWOP Stockton 114 F 0515 PM 08/24 CWOP Riverside 114 F 0346 PM 08/24 CWOP Mount Pleasant 114 F 0330 PM 08/24 MESOWEST University Heights 113 F 0610 PM 08/24 MESOWEST Burlington Arpt 113 F 0353 PM 08/24 ASOS Clinton Arpt 113 F 0156 PM 08/24 AWOS Savanna Arpt 113 F 0458 PM 08/24 AWOS Spring Valley Airport 113 F 0505 PM 08/24 AWS Lone Tree 112 F 0410 PM 08/24 MESOWEST IOWA CITY 112 F 0528 PM 08/24 CWOP Stanley 112 F 0600 PM 08/24 CWOP Dubuque Arpt 112 F 0553 PM 08/24 ASOS Freeport Arpt 112 F 0155 PM 08/24 AWOS Quad City Intl Arpt 112 F 0552 PM 08/24 ASOS Cedar Rapids I-380 112 F 0505 PM 08/24 MESOWEST Independence Arpt 111 F 0355 PM 08/24 AWOS Iowa City I-80 111 F 0545 PM 08/24 MESOWEST Manchester 111 F 0400 PM 08/24 MESOWEST Muscatine 110 F 0430 PM 08/24 CWOP Mount Pleasant Arpt 110 F 1155 AM 08/24 AWOS Dubuque 109 F 0548 PM 08/24 CWOP Iowa City 109 F 0649 PM 08/24 CWOP Cedar Rapids Arpt 109 F 0452 PM 08/24 ASOS Fairfield Arpt 109 F 0415 PM 08/24 AWOS Iowa City Arpt 109 F 0252 PM 08/24 ASOS Anamosa 108 F 0550 PM 08/24 MESOWEST Dubuque 106 F 0448 PM 08/24 CWOP Davenport 106 F 1110 AM 08/24 MESOWEST Maquoketa 106 F 0430 PM 08/24 MESOWEST Victor 106 F 0350 PM 08/24 MESOWEST Dubuque 104 F 0619 PM 08/24 CWOP

Environment


Figure 1: 500 mb Height Loop Courtesy College of DuPage	Figure 2: 500mb Climatology	Figure 3: Freezing Level Climatology


Figure 4: 500 mb Composite Mean showing a substantial anomalous upper ridge sprawling across the central U.S. This kept weather systems and any cooling effects of cloud cover or precipitation well north near the Canadian border. It also provided a substantial atmospheric depth of heat (as shown in Figure 2) across a huge area, resulting in many locations reaching upper 90s to triple digits across the Corn Belt, Mississippi River Valley, and Plains.

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Flash Flooding Likely into Tonight for Portions of Kansas and Missouri; Heat Wave Expands to the East Coast; Tropical Storm Krosa Forms Near the Marianas.

Late Summer 2023 Heat Wave Recap