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Historical record · Iowa

Lake Ice Out and Ice In Dates in Iowa

Iowa's ice record is small and specific: the Iowa Great Lakes in Dickinson County. West Okoboji, East Okoboji and Spirit Lake have been observed since 1916, and all three carry the freeze as well as the thaw.

3
Lakes with a record
40 or more recorded years each
487
Observations
individual dates written down
1916
Oldest observation
East Okoboji Lake
0
Century long records
spanning 100 years or more

Dates from past winters. For today’s ice, ask the agency that manages the water.

Where this year’s dates come from

Iowa publishes no compiled ice-out list. The three records here end in 2008, so treat them as history rather than as a current picture.

Iowa Department of Natural Resources

Today against the record

How this date has usually played out

Where today sits in the record for East Okoboji Lake

40 of 40 of the most recent recorded years had already seen ice out on East Okoboji Lake by this date.

The median across the whole record is April 1, which is 174 days from now on this year’s calendar. The record itself runs to 2008, so this is a comparison against history and not a statement about the current season.

This counts recorded years, not this year; the current season comes from the agency linked above.

Lake by lake

The deepest Iowa records

Ordered by how much record there is behind them. The median is across every recorded year; the second figure is across the most recent 30 recorded years, which is the fairer thing to compare against a lake you know today.

Names are reproduced exactly as the source database records them, which is often a shortened form: a lake filed as “Detroit” or “George” is Detroit Lake or Lake George to everyone who lives on it. The names stay as recorded, because United States lakes split unpredictably between “Lake X” and “X Lake”.

East Okoboji Lake

Lake in Iowa · 93 recorded years, 1916 to 2008record ends 2008

Apr 1
median ice out
Apr 2
last 30 recorded years
Mar 3
earliest, 1931
Apr 26
latest, 1951

Across the whole record, ice out has moved 4 days later per century across the record.

Freeze over has moved barely at all across the record, median Nov 30.

1910sApr 61920sMar 251930sMar 241940sMar 311950sApr 91960sApr 71970sApr 71980sMar 301990sMar 312000sMar 31

Mean date per decade. Only decades with four or more observations are shown, and the scale starts near the shortest bar rather than at January 1, so small differences stay visible.

West Okoboji Lake

Lake in Iowa · 93 recorded years, 1916 to 2008record ends 2008

Apr 6
median ice out
Apr 4
last 30 recorded years
Mar 8
earliest, 2000
Apr 28
latest, 1951

Across the whole record, ice out has moved barely at all across the record.

Freeze over has moved 4 days later per century across the record, median Dec 12.

1910sApr 81920sApr 51930sMar 301940sApr 41950sApr 141960sApr 91970sApr 91980sApr 31990sApr 42000sApr 2

Mean date per decade. Only decades with four or more observations are shown, and the scale starts near the shortest bar rather than at January 1, so small differences stay visible.

Spirit Lake

Lake in Iowa · 65 recorded years, 1944 to 2008record ends 2008

Apr 5
median ice out
Apr 2
last 30 recorded years
Mar 7
earliest, 2000
Apr 28
latest, 1951

The record spans 64 years, under the 80 year span needed to state a century trend.

1940sApr 41950sApr 121960sApr 91970sApr 81980sMar 311990sApr 12000sApr 1

Mean date per decade. Only decades with four or more observations are shown, and the scale starts near the shortest bar rather than at January 1, so small differences stay visible.

A person in a red jacket standing on brown grass at the foot of a wall of shattered lake ice piled far higher than they are
An ice shove on Lake Winnebago in Wisconsin, with a person on the bank for scale. Wind on a rotting spring sheet can drive it ashore in minutes and stack it well above head height, which is one reason a tidy single ice out date hides a genuinely messy few days. “Ice shove - Lake Winnebago, Oshkosh, WI USA - March 2025” by Jm mortellwi, CC BY-SA 4.0
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Every lake

All 3 Iowa water bodies with a long record

LakeRecordMedian ice outLast 30 yearsEarliestLatestChange per century
East Okoboji Lake1916 to 2008 (93)Apr 1Apr 2Mar 3 1931Apr 26 1951+4.4 days
West Okoboji Lake1916 to 2008 (93)Apr 6Apr 4Mar 8 2000Apr 28 1951-0.8 days
Spirit Lake1944 to 2008 (65)Apr 5Apr 2Mar 7 2000Apr 28 1951record too short

Dates are day of year, rendered on a common non leap calendar so the same stored value always reads the same way. “Change per century” is a least squares line through the observations, shown only where a record spans 80 years or more; a century figure extrapolated from a 40 year window describes the decades that happened to be sampled rather than the lake. Where a record ends before 2010 the card says so; a great many of these series stopped when a particular person stopped keeping them.

False colour satellite view of Minnesota in spring, with ice covered lakes showing as pale cyan and lakes that have already opened showing as black, against green and tan land
Spring thaw over Minnesota, in false colour. Ice still on a lake reads pale cyan; a lake that has already opened reads black. You can watch ice out happen across a whole state in a single frame, which is how agencies now sanity check reports that used to come only from people standing on a shore. “Spring Thaw in Minnesota (MODIS 2025-04-30)” — MODIS Land Rapid Response Team, NASA GSFC — Public domain
What the record says

What the Iowa record shows

Of the 2 Iowa lakes with a record long enough to state a century trend, 1 show ice out moving earlier. The median shift across those lakes is 4.4 days per century. That is a description of a line fitted to observations, not a forecast, and any single lake can and does swing three or four weeks between consecutive years.

3 of these Iowa water bodies also carry a freeze over record. Freeze up is the harder half to observe and there is far less of it nationally, which is a shame, because in this dataset it moves more than ice out does.

The Iowa series were contributed to the international ice phenology database by state fisheries staff, and record both the day the lake froze over and the day it opened.

Three lakes, one basin. West Okoboji is deep and clear and holds its ice differently from shallow East Okoboji next door, which is exactly why having all three in one basin on the same record is useful.

Satellite view of the Great Lakes with the northern land still under snow, the lakes themselves dark open water, and pale green sediment plumes in the shallow western basin of Lake Erie
The Great Lakes with snow still lying on the land north of them and no ice left on the water. On a lake this size, freezing over and opening are not single moments: shallow bays close first, the deep middle may never freeze at all in a mild winter, and the date somebody writes down is a judgement call. “Spring Thaw across the Great Lakes (MODIS)” — MODIS Land Rapid Response Team, NASA GSFC — Public domain
Provenance

Where these Iowa numbers came from

The observations

Benson, B., Magnuson, J. and Sharma, S. (2000). Global Lake and River Ice Phenology Database. (G01377, Version 1). Boulder, Colorado USA. National Snow and Ice Data Center. https://doi.org/10.7265/N5W66HP8 Accessed 2026-08-24.

All three Iowa records begin in 1916 and end in 2008, so they describe most of the twentieth century and none of the last fifteen years.

Common questions

Iowa lake ice FAQ

A wide historical panorama of a lake shore with wooded banks, boats and a low pavilion at the water line
Iowa water. Ice out is the day this becomes possible again, and in most of these records it is the day somebody decided a boat could cross. “Head of West Okoboji Lake LCCN2013645032” — Williamz, L. F. (Lucius F.), copyright claimant — Public domain
The rest of the Iowa year

Plan the rest of your Iowa calendar

Iowa lake ice inThe autumn half of the same records: when these lakes have typically frozen over. Together the two are the length of the ice season.Every state with a lake ice recordThe national picture: every state with a lake ice record and the deepest series in the country.Iowa winter outlookWhat NOAA expects from the season that puts the ice on.Iowa fall foliageThe other end of the year on the same water.

More Midwest states with lake ice records

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Ice out and ice in dates are historical observations compiled by the National Snow and Ice Data Center and, for the New England lakes, by the U.S. Geological Survey. They describe past years only, and a past year says nothing about the ice on a lake today. For current ice and for anything involving going out on it, contact Iowa Department of Natural Resources. National picture: every state with a lake ice record →
Hero image: “Head of West Okoboji Lake LCCN2013645032” — Williamz, L. F. (Lucius F.), copyright claimant — Public domain