IEM Daily Bulletin for Sep 10 2025

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 10 September 2025

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
Sep 9 8:46 AM	iem,main	✨ Implement throttle to keep from getting overrun	Link
Sep 9 7:49 PM	pyiem,main	✨ Add method=head to archive_fetch	Link
Sep 9 7:49 PM	pyiem,main	⬆️ Update ruff	Link

Daily Feature

Earliest Sub 37°F Low
Date: 09 Sep 05:30 AM
Votes: Good: 19   Bad: 1 Abstain: 0

Sioux City set a record low Sunday morning of 36°F, breaking the previous record of 38°F set in 1986. This was also the earliest date for such a cool temperature for the site on record with archives going back to 1889! The featured chart presents the yearly period between the last spring season and first fall season date with a low temperature below 37°F. The yearly time series of dates is fit with a trend line, simple average, and trailing 30 year average. The recent trend and fit lines don't indicate much change for this metric over the period of record.

The featured media can be generated on-demand here

.

NWS Watch/Warning Summary for 12 AM 9 Sep 2025 - 12 AM 10 Sep 2025 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	0	0	0	0	0	0	0	0
Svr Tstorm	57	0	0	0	0	3	0	1
Flash Flood	10	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:   8 [14.8%]
Polygon Size Versus County Size            [12.7%]
Average Perimeter Ratio                    [16.7%]
Percentage of Warned Area Verified (15km)  [7.3%]
Average Storm Based Warning Size           [925 sq km]
Probability of Detection(higher is better) [0.68]
False Alarm Ratio (lower is better)        [0.85]
Critical Success Index (higher is better)  [0.14]