Frost dates for Des Moines, Iowa
In Des Moines, half of springs have had their last frost by April 18 (and 1 spring in 10 still has one after May 2), and half of falls have had their first frost by October 20, leaving about 184 frost-free days in a typical year. Here is how sure those dates are, what they mean for planting, and where they come from.
Frost dates for
Des Moines, Iowa
Last spring frost
April 18
Half of springs have their last frost by this date. For a safer bet, wait until May 2: only 1 spring in 10 has a frost after that.
First fall frost
October 20
Half of falls have their first frost by this date. In 1 fall in 10 it comes by October 4.
Growing season
184 days
Frost-free days in a typical year. 9 years in 10 get at least 165.
Hardiness zone
5b
2023 USDA map: the coldest night of winter averages −15°F to −10°F. It was 5b on the 2012 map too. All 13 ZIP codes within about 6 miles of the city's center are in zone 5b.
Print a year planner for Des Moines
Frost risk through the year
How sure are these dates?
A frost date is a probability, not a promise. NOAA worked out, from 30 years of nightly lows, how often the last spring frost and the first fall frost fall on each date. The middle column is the typical year. The outer columns are the early and late years that come about once a decade.
| Early year 1 in 10 | Typical year 1 in 2 | Late year 1 in 10 | |
|---|---|---|---|
| Last frost in spring | April 4 | April 18 | May 2 |
| First frost in fall | October 4 | October 20 | November 1 |
The frost-free season between them runs 184 days in a typical year. In 1 year in 10 it is 203 days or longer, and in 1 year in 10 it is 165 days or shorter.
- Hard freeze (28°F): typically last on April 8 and first on October 30. It is a harder freeze than the 32°F frost line, cold enough to damage many garden plants; how hardy a crop is decides whether it comes through. (The National Weather Service's own hard-freeze threshold varies from office to office.)
- Frost possible (36°F at the station): typically last on April 29 and first on October 9. On clear, still nights the ground can be several degrees colder than the thermometer, so frost can form on plants when the official reading is in the mid-30s.
In 8 springs out of 10, the last frost in Des Moines comes between April 4 and May 2, a window of 28 days. That is about average for NOAA's stations (the typical window is 31 days).
Among Iowa's 150 NOAA stations with a frost every year, 91 percent have their typical last frost later than Des Moines does.
Planting calendar for Des Moines
These dates count from the typical last and first frosts, using the planting rules published by Colorado State University Extension (spring), Virginia Cooperative Extension (fall crops) and University of Minnesota Extension (garlic, where winters are hard). Weather in any one year can run early or late, so check the forecast before you plant tender crops.
| When | What to do | Why then |
|---|---|---|
| January | ||
| January 31 to February 28 | Broccoli and cabbage Start seeds indoors | 5 to 7 weeks before planting them out |
| February | ||
| February 14 to March 14 | Cauliflower Start seeds indoors | 5 to 7 weeks before planting out |
| February 28 to March 21 | Eggplant Start seeds indoors | 6 to 9 weeks before planting out |
| March | ||
| March 7 to 21 | Peppers Start seeds indoors | 6 to 8 weeks before planting out |
| March 14 to 28 | Tomatoes Start seeds indoors | 5 to 7 weeks before planting out |
| March 21 to April 4 | Peas, spinach, lettuce, radishes, onion sets, turnips Sow outdoors, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| March 21 to April 4 | Broccoli and cabbage Plant out, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| April | ||
| April 4 to 18 | Beets, carrots, potatoes, Swiss chard Plant outdoors, as early as | semi-hardy crops: up to 2 weeks before the typical last frost |
| April 4 to 18 | Cauliflower Plant out, as early as | semi-hardy: up to 2 weeks before the typical last frost |
| April 18 | Snap beans, sweet corn, cucumbers, summer squash Sow outdoors around | tender crops: around the typical last frost date |
| May | ||
| May 2 | Tomatoes, peppers, eggplant Plant out from | very tender: 2 weeks or more after the typical last frost |
| May 2 | Melons, winter squash, pumpkins, lima beans Sow outdoors from | very tender: 2 weeks or more after the typical last frost |
| May 25 to June 8 | Cabbage for fall Start seeds | set the plants out by July 13 |
| June | ||
| June 14 to 28 | Broccoli for fall Start seeds | set the plants out by August 2 |
| July | ||
| July 24 | Snap beans for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| July 28 | Carrots for fall Last date to sow | 70 days to harvest, plus 2 weeks for slower fall growth |
| July 29 | Cucumbers for fall Last date to sow | 55 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August | ||
| August 2 | Peas for fall Last date to sow | 65 days to harvest, plus 2 weeks for slower fall growth |
| August 3 | Summer squash for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August 7 | Leaf lettuce and beets for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth |
| August 17 | Turnips and kohlrabi for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth |
| August 27 | Spinach for fall Last date to sow | 40 days to harvest, plus 2 weeks for slower fall growth |
| September | ||
| September 6 | Radishes for fall Last date to sow | 30 days to harvest, plus 2 weeks for slower fall growth |
| October | ||
| October 4 | Tomatoes, peppers, squash, melons, cucumbers Watch the forecast from | in 1 fall in 10 the first frost comes by this date; pick tender crops before a frost |
| November | ||
| November 6 to 13 | Garlic Plant cloves | one or two weeks after the typical first hard freeze (28°F), our reading of the first killing frost |
Want more insurance? Shift every spring date 14 days later. That plans around May 2, the date after which only 1 spring in 10 has a frost.
For spring bulbs such as tulips and daffodils, plant once the soil has cooled to about 50 to 55°F and keep going until a couple of weeks before the ground freezes. Our guide to fall planting explains how to tell.
Where these numbers come from
These dates come from NOAA's weather station Des Moines International Airport (station USW00014933), 3 miles from the center of Des Moines. It sits 140 feet higher, at 960 feet above sea level. NOAA rates this station's record as standard: at least 24 of the 30 years, with gaps filled from nearby stations.
The same station also gives the frost dates for West Des Moines, Urbandale, Waukee, Johnston, Altoona, Clive, Grimes and Norwalk.
Our ZIP code lookup matches these 18 ZIP codes to the same station, so they get the same dates: 50038, 50061, 50265, 50266, 50309, 50310, 50311, 50312, 50314, 50315, 50316, 50317, 50319, 50320, 50321, 50324, 50325, 50327. Hardiness zones are worked out separately for each ZIP code.
The nearest other places with pages
- Cedar Rapids, Iowa: last frost around April 27, first frost around October 11 (105 miles away)
- Bellevue, Nebraska: last frost around April 18, first frost around October 21 (125 miles away)
- Omaha, Nebraska: last frost around April 16, first frost around October 18 (130 miles away)
See frost dates across Iowa, or look up your own ZIP code for the station nearest you. Want the background? Read what a last frost date really means.