IEM Daily Bulletin for Jul 28 2026
daryl herzmann
Iowa Environmental Mesonet Daily Bulletin for 28 July 2026
News
Title: 26-27 July 2026 Record Dew Points
Date: 27 Jul 08:08 PM
Author: Daryl Herzmann
link
A historically humid air mass brought record high dew point temperatures to a number of locations within Iowa and beyond. The National Weather Service does not officially track record dew point temperatures nor do the ASOS airport weather stations report a maximum daily aggregated value, so what follows is based on unofficial IEM period of record archives of hourly reports from NOAA/NWS. Please note some of these sites set records on the day before, 25 July 2026.
| State | ID | Name | Data Since | 26 July 2026 Max °F | 27 July 2026 Max °F | Most Recent Day as High | Current/Previous Record °F | Most Recent Date of Record |
|---|---|---|---|---|---|---|---|---|
| IA | AMW | Ames | 1996 | 86 | 82 | - | 82 | 2016 Aug 4 |
| IA | BRL | Burlington | 1931 | 85 | 84 | -- | 82 | 2015 Jul 13 |
| SD | BKX | Brookings | 1973 | 81 | 79 | 1985 Jun 25 | 82 | 1983 Jul 19 |
| IA | CID | Cedar Rapids | 1973 | 83 | 84 | 2016 Jul 23 | 87 | 1995 Jul 13 |
| IA | DBQ | Dubuque | 1951 | 82 | 83 | -- | 82 | 2023 Aug 23 |
| IA | DSM | Des Moines | 1928 | 81 | 83 | -- | 82 | 1997 Jul 26 |
| MN | DLH | Duluth | 1940 | 76 | 70 | 2011 Jul 17 | 78 | 2003 Aug 24 |
| IA | DVN | Davenport | 1996 | 81 | 82 | 2024 Jul 15 | 83 | 1999 Jul 29 |
| IA | EST | Estherville | 1987 | 83 | 80 | 2011 Jul 18 | 84 | 2011 Jul 18 |
| SD | FSD | Sioux Falls | 1932 | 81 | 80 | 2016 Jul 11 | 82 | 2016 Jul 11 |
| MN | FRM | Fairmont | 1973 | 84 | 80 | -- | 83 | 1985 Sep 6 |
| SD | HON | Huron | 1940 | 79 | 78 | 2011 Aug 2 | 81 | 2011 Jul 18 |
| IA | IOW | Iowa City | 1996 | 83 | 84 | 1998 Aug 20 | 84 | 1998 Aug 20 |
| IA | MCW | Mason City | 1941 | 81 | 82 | 2011 Jul 19 | 83 | 1999 Jul 29 |
| IA | MIW | Marshalltown | 1996 | 83 | 83 | 2016 Jul 23 | 83 | 2016 Jul 23 |
| MN | MML | Marshall | 1984 | 80 | 77 | 2026 Jul 25 | 82 | 2011 Jul 18 |
| SD | MHE | Mitchell | 1973 | 81 | 80 | 2022 Jun 13 | 84 | 2002 Jul 14 |
| MN | MKT | Mankato | 1973 | 83 | 81 | 1986 Jul 18 | 84 | 1986 Jul 18 |
| WI | MSN | Madison | 1939 | 77 | 79 | 2023 Aug 24 | 81 | 2023 Aug 23 |
| MN | OTG | Worthington | 1973 | 84 | 81 | 1977 Jul 16 | 84 | 1977 Jul 16 |
| IA | OTM | Ottumwa | 1940 | 83 | 80 | --- | 82 | 2015 Jul 28 |
| MN | MSP | Minneapolis | 1931 | 78 | 81 | 2019 Jul 19 | 82 | 2011 Jul 19 |
| IL | SPI | Springfield | 1935 | 84 | 79 | -- | 83 | 2023 Aug 25 |
| IA | SPW | Spencer | 1973 | 82 | 78 | 2011 Jul 18 | 83 | 2011 Jul 18 |
| IA | SUX | Sioux City | 1939 | 83 | 80 | 2026 Jul 25 | 83 | 2026 Jul 25 |
| SD | YKN | Yankton | 1973 | 82 | 81 | 2026 Jul 25 | 84 | 2026 Jul 25 |
Related Links
- Autoplot 153 lists hourly maximum dewpoints over the period of record.
- Autoplot 140 computes daily statistics, like number of days with a max dew point above 80°F by year.
- ASOS Download Portal
IEM Code Pushes <repo,branch> on Github
| Timestamp | Repository | Message | Link |
|---|---|---|---|
| Jul 27 7:28 AM | iem,main | 📝 Address some lint | Link |
| Jul 27 10:41 AM | iem,main | 🎨 Conditionally update {min,max}_tmpf as well | Link |
| Jul 27 10:50 AM | iem,main | 🩹 Stop auto-submission of date field | Link |
| Jul 27 10:55 AM | iem,main | 📝 Improve 429 error message to user | Link |
| Jul 27 12:01 PM | iem,main | 📝 Sundry review of yieldfx codes | Link |
Daily Feature
Iowa Max Dew Points
Date: 27 Jul 05:30 AM
Votes: Good: 28
Bad: 2 Abstain: 0
Sunday was incredibly hot and humid over Iowa with afternoon dew point temperatures in the low 80s and air temperatures in the 90s! The featured info-graphic presents IEM computed maximum dew point temperatures on Sunday along with period of record maximums based on unofficial IEM archives of NOAA/NWS data. There are many caveats to this type of analyses as true daily maximum dew point temperatures are not something officially reported nor curated by the NWS. The long term archive is based on mostly hourly reports. Additionally, stations have changed instrumentation, observation techniques, and local surrounding vegetation over the years. All of these items make period of record comparisons problematic. This graphic also is limited to the long term airport sites that are federally maintained. You may have seen other reports about Iowa denoting dew point readings reaching 90°F at state maintained airport stations on Sunday. These values are very likely in error. So having said all of that, three of the listed sites (Ames, Burlington, and Ottumwa) hit period of records on Sunday. Monday will be another very hot and humid day, but hopefully a few degrees less humid than Sunday!
NWS Watch/Warning Summary for 12 AM 27 Jul 2026 - 12 AM 28 Jul 2026 CDT
| Summary | By WFO | Watches | ||||||
|---|---|---|---|---|---|---|---|---|
| Type | US | IA | ARX | DVN | DMX | OAX | FSD | US |
| Tornado | 22 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Svr Tstorm | 257 | 0 | 0 | 0 | 0 | 0 | 0 | 7 |
| Flash Flood | 46 | 0 | 0 | 0 | 0 | 0 | 0 | --- |
ARX = LaCrosse, WI DVN = Davenport, IA DMX = Des Moines, IA OAX = Omaha, NE FSD = Sioux Falls, SD
IEM Cow Report
SVR+TOR Warnings Issued: 275 Verified: 125 [45.5%] Polygon Size Versus County Size [24.6%] Average Perimeter Ratio [33.0%] Percentage of Warned Area Verified (15km) [25.1%] Average Storm Based Warning Size [1281 sq km] Probability of Detection(higher is better) [0.80] False Alarm Ratio (lower is better) [0.55] Critical Success Index (higher is better) [0.41]
IEMBot Social Media Posts
IEMBot can be configured to post messages to a number of social media services. More details: IEMBot Homepage.
Posts yesterday per supported service:
- ATMosphere (bluesky only attm): 2,973
- Mastodon / Fediverse: 99
- Slack: 3,464
- Twitter/X: 12,893
- HTTP Webhooks: 618
- Weather.IM Jabber Chatrooms: 20,990