IEM Daily Bulletin for Dec 5 2025

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 05 December 2025

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
Dec 4 12:42 PM	iem,main	🔥 Unbundle mapserv binary, cover with apache cfg	Link
Dec 4 12:43 PM	iem,main	⬆️ Update ruff	Link
Dec 4 1:14 PM	iem,main	🐛 Address dbquery construction	Link
Dec 4 10:59 PM	iem,main	🐛 Address mapserv paths in other places, oopsy	Link

Daily Feature

First Fall Cold Lows
Date: 04 Dec 05:30 AM
Votes: Good: 8   Bad: 1 Abstain: 0

After a mild start on Wednesday morning, an arctic front swept the state and ushered in much colder temperatures and the coldest air of the season to date. Low temperatures this Thursday morning are well below zero and likely record lows for today for many sites in the state. The featured chart looks into the accumulated frequency of having the season's first low temperature of the given threshold by the given date of the season for Ames. The chart plots as a percentile over all years, so there are some years that failed to reach the given threshold and that is why the accumulated value does not reach 100 in all cases. The side table shows the percentile dates for each threshold. Having such cold weather by 4 December comes in around the 10-25th percentile of so, so about once or twice per decade to experience such cold temperatures this early for the given thresholds plotted.

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 4 Dec 2025 - 12 AM 5 Dec 2025 CST

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	0	0	0	0	0	0	0	0
Svr Tstorm	0	0	0	0	0	0	0	0
Flash Flood	1	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

No SVR+TOR Warnings Issued.