Iowa Environmental Mesonet Daily Bulletin for 29 August 2026

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp Repository Message Link
Aug 28 9:59 AM iem,main 🐛 Fix input tzinfo sanitation with RWIS download Link
Aug 28 9:59 AM iem,main ⬆️ Update ruff precommit Link
Aug 28 12:18 PM iem,main 🐛 Fix logic bugs with freezing dates list
https://mesonet.agron.iastate.edu/COOP/freezing.php
Link
Aug 28 12:19 PM iem,main ✅ Test and permit RWIS requests without hr,mi Link
Aug 28 9:25 PM iem,main 🎨 Sundry churn and coverage improvements Link
Aug 28 9:35 PM iem,main 💚 Address codereview Link
Aug 28 2:59 PM pyiem,main 🐛 Account for iemapp(default_tz) for sts/ets gen
closes #1248
Link
Aug 28 3:18 PM pyiem,main 🎨 Cleanup tz usage per codereview Link
Aug 28 3:32 PM pyiem,main 💚 Address coverage hit Link
Aug 28 5:28 PM pyiem,main 💚 Add suggested test Link
Aug 28 11:07 AM pywwa,main 🎨 Remove forced non-https with send_message
Also addresses coverage hit from previous PR
Link
Aug 28 10:34 AM iem-database,main 🎨 Ensure LSR geoms are not null Link
Aug 28 10:36 AM iem-database,main ⬆️ Update ruff precommit Link


Daily Feature

Warning/Advisory Climatology
Date: 28 Aug 05:30 AM
Votes: Good: 13   Bad: 0 Abstain: 1

One of the most popular and seemingly internet unique datasets curated by the IEM is an archive of National Weather Service Watch, Warnings, and Advisories. This archive became tenable with the implementation of VTEC within the raw text products during the mid to late 2000s. So with about a 20 year archive of data, climatologies are possible! The featured chart is from a newly added "Autoplot" that computes the monthly average number of NWS Warnings/Advisories by month for Story County (Ames, IA). These alerts are grouped into general categories. Without getting too far off in the weeds here, the NWS issues some of these products for forecast zones and some for counties. Within Iowa, these are the same geographic regions, but this is not the case for most states. So to get reliable stats, the chart combines the "county" and "forecast zone" that covers Story County. The purpose of the chart is to highlight the seasonality of various alert categories and also provide a sense of frequency. Note that this chart does not include watches, but only warnings and advisories. June is clearly the most frequent month for Severe Thunderstorm Warnings, but May is for Tornado Warnings. January is the overall "winner" for most events on average with September having the least. You can generate this chart by NWS forecast office, state, and even FEMA region. Feedback is certainly welcome!

The featured media can be generated on-demand here

.

NWS Watch/Warning Summary for 12 AM 28 Aug 2026 - 12 AM 29 Aug 2026 CDT

Summary By WFO Watches
Type USIA ARXDVNDMXOAXFSD US
Tornado 0 0 0 0 0 0 0 0
Svr Tstorm 56 0 0 0 0 0 0 0
Flash Flood 23 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:  54 Verified:  24 [44.4%]
Polygon Size Versus County Size            [17.9%]
Average Perimeter Ratio                    [22.4%]
Percentage of Warned Area Verified (15km)  [23.1%]
Average Storm Based Warning Size           [1603 sq km]
Probability of Detection(higher is better) [0.77]
False Alarm Ratio (lower is better)        [0.56]
Critical Success Index (higher is better)  [0.39]

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