IEM Daily Bulletin for Jul 30 2026

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 30 July 2026

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
Jul 29 3:02 PM	iem,main	🎨 Prevent checkbox UI wrapping	Link
Jul 29 3:03 PM	iem,main	🚧 Add some vars to ISUSM homepage/backend	Link
Jul 29 3:40 PM	iem,main	🐛 Protect dwpf calculation	Link
Jul 29 12:38 PM	iem-web-services,main	⬆️ Update ruff precommit	Link

Daily Feature

Maximum Heat Index
Date: 29 Jul 05:30 AM
Votes: Good: 13   Bad: 0 Abstain: 0

While still quite humid, Tuesday felt much better than the oppressive humidity of the previous two days. Humidity levels, as measured by dew point temperature, were at or close to period of record maximum values for a number of airport stations over Iowa and beyond. It stands to reason that the heat index was at near record values as well. The featured chart presents the top 10 dates for maximum heat index for Des Moines. Only the highest value each day is plotted once, so this list isn't the top ten hourly heat index values, but top ten dates for highest heat index value. Anyway, Sunday and Monday are both shown on this list with Monday's 119.7°F (Temp: 94°F, Dew Point: 83°F) coming in second place. As an aside, the National Weather Service continues to work toward replacing heat index usage with an index called Wet Bulb Globe Temperature (WBGT), which takes more weather variables into account. The replacement is still more than a year or more away.

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 29 Jul 2026 - 12 AM 30 Jul 2026 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	88	0	0	0	0	0	0	1
Flash Flood	64	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:  88 Verified:  38 [43.2%]
Polygon Size Versus County Size            [15.0%]
Average Perimeter Ratio                    [15.9%]
Percentage of Warned Area Verified (15km)  [19.5%]
Average Storm Based Warning Size           [1998 sq km]
Probability of Detection(higher is better) [0.76]
False Alarm Ratio (lower is better)        [0.57]
Critical Success Index (higher is better)  [0.38]

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