IEM Daily Feature
Friday, 22 October 2021
Friday, 22 October 2021
First Freeze Hour
Posted: 22 Oct 2021 05:34 AM
Based on hourly temperature reports from the Des Moines Airport, the featured chart presents the
frequency of a given hour reporting the first fall temperature below 32 degrees. Note, all events are
presented in Central Daylight Time to rectify the dataset. The midnight to 8 AM period is the obvious
preferred time as these events are almost always driven by accumulated radiational cooling and the
time for such cooling is when sunshine is not present and a number of hours after the sun set for the
previous day. An interesting outlier is highlighted that happened just last year! The first event for 2020
happened with the 11 AM observation on 19 October. You may recall the wild weather we had then
with a major early season snowfall impacting the state. So far this morning, Des Moines has remained
above freezing but there is still time before the sun rises and we'll take another run at freezing Saturday
morning.
Voting:
Good = 21
Bad = 2
Voting:
Good = 21
Bad = 2