IEM Daily Bulletin for Sep 26 2025

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 26 September 2025

News

No news is good news

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Daily Feature

September streaks above 57°F
Date: 25 Sep 05:30 AM
Votes: Good: 7   Bad: 0 Abstain: 0

Our current stretch of September weather has been persistently mild without much of any chilly weather to speak of since the 7th. Des Moines has not had a temperature below 57°F since the morning of the 8th and that streak is the subject of today's featured chart. The chart presents the top 10 longest such streaks during September based on available hourly temperature reports from the airport. The current streak, which perhaps has some risk of ending later this Thursday morning, comes in fourth longest on record. If this morning's hourly low stays above 57°F, the current forecast has a number of days upcoming with temperatures above this arbitrary threshold value. Will update this feature later this morning to see how cold the hourly reports got!

Updated: The hourly temps reached 55°F this morning, so this streak did end!

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 25 Sep 2025 - 12 AM 26 Sep 2025 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	4	0	0	0	0	0	0	0
Svr Tstorm	38	0	0	0	0	0	0	0
Flash Flood	21	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:  40 Verified:  12 [30.0%]
Polygon Size Versus County Size            [5.0%]
Average Perimeter Ratio                    [13.7%]
Percentage of Warned Area Verified (15km)  [14.4%]
Average Storm Based Warning Size           [954 sq km]
Probability of Detection(higher is better) [0.58]
False Alarm Ratio (lower is better)        [0.70]
Critical Success Index (higher is better)  [0.25]