Des Moines, IA Frost Dates: Last Spring and First Fall Frost

The last spring frost in Des Moines, IA comes on April 18 in a typical year, and the first fall frost follows on October 20, leaving a frost-free season of 184 days.

Because half of all years do worse than the typical date, the dates that matter for tender plants are the late spring date, May 2, and the early fall date, October 4, each of which one year in ten fails to beat. Against the 100-city median of 229 days, Des Moines has 45 days less room before frost returns.

NOAA measured them at Des Moines International AP (station USW00014933), about 3.5 miles south-west of the Census Bureau's internal point for Des Moines and about 960 feet above sea level.

Last spring frost in Des Moines

Frost is still possible on April 4 in nine springs out of ten and on April 18 in five; only one spring in ten sees a freeze as late as May 2.

The early and late dates sit just 28 days apart, narrower than for most cities on these pages. Spring in Des Moines rarely surprises by much.

When is the first frost in Des Moines?

NOAA's early fall date for Des Moines is October 4, its even-odds date is October 20 and its late date is November 1; the first freeze has come by each of them in one, five and nine years out of ten.

Just 28 days separate the early and late dates, tighter than most cities on these pages.

The growing season in Des Moines

A little less room than the middle of these pages, so count the days before you choose a variety. A short year costs just 19 days against a typical one (165 days against 184 days), so a season-length plan for Des Moines holds up in most years.

These figures are NOAA's own counts of freeze-free days across its simulated years, which is why they can differ a little from the days between the two typical dates. A night at or below 32°F happens in 100% of years at this station, so frost is a yearly event here.

28°F dates in Des Moines

Between a light frost and a hard freeze there is little room in Des Moines: the typical 28°F dates are October 30 and April 8, just 10 days and 10 days from the 32°F dates. At the edges, a 28°F night on or after April 22 happens one spring in ten and one by October 16 one fall in ten; the nine-in-ten dates are March 25 and November 11.

Using Des Moines's frost dates in the garden

In Des Moines the University of New Hampshire Extension count lands like this, measured from the typical last frost on April 18: lettuce from March 21 to March 28, cabbage on March 21, seed potatoes from April 4 to April 11, then peppers on May 2 and beans from April 18. Peas are the exception to the count: University of New Hampshire Extension says to plant them as soon as the soil thaws, whatever the frost date.

The late date comes 14 days after the typical one; choose it for plants you cannot cover.

Of the 34 crops in the fall planner, 25 still have a July-or-later last planting day in Des Moines once NC State Extension's days to harvest and University of Georgia Extension's harvest allowance of 18 days are counted back from frost. The other 9 do not. Of the crops that fit, cabbage is the slowest: 93 days from planting to the early frost, which makes July 3 its last day.

Worked example: setting out tomatoes in Des Moines

Take tomatoes in Des Moines. The University of New Hampshire Extension rule is to set transplants out one to two weeks after the last frost. From April 18, the typical date, that means April 25 to May 2; from May 2, the late date, it means May 9 to May 16, a delay of 14 days.

Indoors, tomato seeds go in six to eight weeks ahead of set-out; from the first day of the late window that is March 14 to March 28.

Between the last set-out day and the early first frost on October 4 lie 141 days. Tomatoes need 75 to 85 days by NC State Extension's count, so the schedule has 56 days of slack even in an early-frost year.

The weather station behind these dates

The station is 3.5 miles south-west of the Census Bureau's internal point for Des Moines, near enough to be the city's reference record, though not in the same yard.

NOAA lists it at about 960 feet, higher than 67 and lower than 32 of the 100 stations in this set. NOAA flags this station's record as standard, the code S, for the data behind its 50% last-frost value.

The Census Gazetteer gives no elevation for Des Moines itself, so this page cannot tell you whether your garden sits above or below the station. If it is noticeably higher or lower, compare the stations the frost dates tool lists nearby and lean toward the colder reading.

How Des Moines's frost dates compare

Of the cities on these pages, Omaha, NE is closest to Des Moines at 128 miles, with two more farther out; none is a close neighbor.

• Omaha, NE (128 miles, west): its last frost is nearly the same as Des Moines's, and frost-free days differ from Des Moines's by less than a week. Its typical dates are April 16 and October 18, with 183 days frost-free.
• Lincoln, NE (168 miles, west): its last frost comes 6 days after Des Moines's, and the frost-free season is 13 days shorter than Des Moines's. Its typical dates are April 24 and October 13, with 171 days frost-free.
• Kansas City, MO lies 176 miles south of Des Moines. Typical last frost April 4, first frost November 2, 211 days between; spring frost ends 14 days sooner than in Des Moines, and the season runs 27 days longer.

Take these dates further

To go beyond the crops above, use the spring planting planner and fall planting planner, both set to this station. The frost dates tool shows the full odds for Des Moines, and the hardiness zone lookup gives the winter-cold zone for your ZIP code.

All the cities on these pages are listed by state on the city frost dates index.

Where these numbers come from

NOAA's U.S. Climate Normals for 1991–2020 (doi:10.25921/4ek7-fk11) supply every frost date here, unchanged from the station's record, and NOAA's documentation defines the probabilities. The Census Bureau's 2024 Gazetteer places Des Moines on the map, and its Vintage 2024 estimates, 213,096 people here, decide which cities get a page.

The planting dates apply the count rules in University of New Hampshire Extension, NC State Extension and University of Georgia Extension to this station's dates, with nothing added. Our methodology describes the tests behind every number.

These dates describe odds over many years, not next week's weather. Look at the forecast before you plant, and keep a sheet or row cover ready for a night that does not follow the odds.