IEM Daily Bulletin for Sep 9 2025

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 09 September 2025

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
Sep 8 10:40 AM	iem,main	📝 Sundry updates per review	Link
Sep 8 10:43 AM	iem,main	💚 Address deepsource concerns	Link
Sep 8 9:57 PM	iem,main	📝 Sundry updates	Link

Daily Feature

Dip Into the 30s
Date: 08 Sep 05:30 AM
Votes: Good: 10   Bad: 0 Abstain: 0

The first full weekend of September featured a considerable taste of the fall season with temperatures dipping into the 30s over most of northern Iowa. The featured map presents a minimum temperature analysis of 15 minute interval NOAA RTMA data covering Saturday and Sunday morning. Iowa avoided any freezing temperatures, but a number of record low temperatures were set, including Sioux City and Ottumwa. Temperatures are forecast to rebound this week with a change of reaching 90 degrees by the end of the week!

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 8 Sep 2025 - 12 AM 9 Sep 2025 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	13	0	0	0	0	0	0	0
Svr Tstorm	60	0	0	0	0	0	0	1
Flash Flood	15	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:  70 Verified:  21 [30.0%]
Polygon Size Versus County Size            [16.2%]
Average Perimeter Ratio                    [24.2%]
Percentage of Warned Area Verified (15km)  [18.0%]
Average Storm Based Warning Size           [915 sq km]
Probability of Detection(higher is better) [0.92]
False Alarm Ratio (lower is better)        [0.70]
Critical Success Index (higher is better)  [0.29]