Iowa Environmental Mesonet Daily Bulletin for 01 September 2026

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp Repository Message Link
Aug 31 8:02 AM iem,main 🎨 Account for yet another ACIS edge case, sigh Link
Aug 31 8:11 AM iem,main 🎨 Use requests and better handle exception Link
Aug 31 8:39 AM iem,main 🎨 Address issues found in prod Link
Aug 31 11:41 AM iemlsr,main ⬆️ Update ruff precommit Link
Aug 31 11:42 AM iemlsr,main ⬆️ Update npm deps Link
Aug 31 11:50 AM iemlsr,main 🎨 Improve accessibility Link
Aug 31 11:52 AM iemlsr,main 🎨 Address vite config issue Link


Daily Feature

Slow Decline
Date: 31 Aug 05:30 AM
Votes: Good: 17   Bad: 0 Abstain: 0

The signs of fall are pretty much everywhere now with even the calendar about to turn into September tomorrow, but the first week of the new month will very much feel like mid summer. The full pull of fall climatology does not arrive for a number of weeks yet as illustrated by the featured map. The map presents the weekly change in high temperature climatology between 31 August to 7 September. Values are rather meager with Iowa shown in the 1 to 2 degrees of cooling over this period. Some of the reasons why summer can stick into September include ample sunshine, elevated humidity levels, active vegetation, and warm soils that take a while to cool off.

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 31 Aug 2026 - 12 AM 1 Sep 2026 CDT

Summary By WFO Watches
Type USIA ARXDVNDMXOAXFSD US
Tornado 0 0 0 0 0 0 0 0
Svr Tstorm 39 0 0 0 0 0 0 0
Flash Flood 30 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:  39 Verified:   3 [7.7%]
Polygon Size Versus County Size            [7.6%]
Average Perimeter Ratio                    [11.0%]
Percentage of Warned Area Verified (15km)  [4.7%]
Average Storm Based Warning Size           [1391 sq km]
Probability of Detection(higher is better) [0.36]
False Alarm Ratio (lower is better)        [0.92]
Critical Success Index (higher is better)  [0.07]

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