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Frost dates and planting calendar for Des Moines, Iowa

Updated October 30, 2026. Based on USDA, NOAA and Colorado State University Extension data. Published by Humblebee.

USDA hardiness zone
5b[1]
Median last spring frost
Apr 18[2]
Median first fall frost
Oct 20[3]
Growing season, median
184 days[4]

Des Moines is in USDA hardiness zone 5b[1]. The median last spring frost is April 18, so in half of years the last frost comes after that date[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Apr 4, half of years Apr 18, 1 in 10 years after May 2Last frostmedian Apr 18First fall frost: 9 in 10 years before Nov 1, half of years Oct 20, 1 in 10 years before Oct 4First frostmedian Oct 20Frost riskHardyHardy vegetables: plant Mar 21 to Apr 4Mar 21 to Apr 4Semi-hardySemi-hardy vegetables: plant Apr 4 to Apr 18Apr 4 to Apr 18TenderTender vegetables: plant around Apr 18around Apr 18Very tenderVery tender vegetables: plant from May 2from May 2
Shaded: the span between the dates frost passes in 9 of 10 years and 1 of 10 years[2][3]. Green: planting windows from the CSU rules applied to the median last frost (GardenFacts calculation)[6]. Exact dates are in the tables below.

These frost dates come from NOAA climate normals for the Des Moines International Airport weather station, using records from 1991 to 2020[5]. In 9 of 10 years the last spring frost comes after April 4, and in 1 of 10 years it comes after May 2[2]. In half of years the first fall frost comes before October 20[3]. In 1 of 10 years it comes before October 4[3]. These are odds from past years and not a forecast, so any year can be earlier or later[5].

Frost Likely (9 in 10 years) Even odds (5 in 10) Unlikely (1 in 10)
Last spring frost (32°F)[2] after April 4 after April 18 after May 2
First fall frost (32°F)[3] before October 4 before October 20 before November 1
  • Hard freeze (28°F): median last spring date April 8, median first fall date October 30[7].
  • Frost-free growing season: at least 165 days in 9 of 10 years, 184 days in half of years and 203 days in 1 of 10 years[4].
  • The low reached 32°F or colder in 100% of years and 28°F or colder in 100% of years[8].
  • Weather station: Des Moines International Airport (USW00014933), 3.5 miles from the city center, 957 feet, 26 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension wrote its vegetable planting guide for Colorado, so treat these dates as a starting point[6]. We use the NOAA median last frost of April 18 as the average last frost[6]. Hardy vegetables such as broccoli, lettuce, peas and spinach can go in as early as 2 to 4 weeks before it, which is March 21 to April 4[6]. Semi-hardy vegetables such as carrots, potatoes and beets can go in as early as April 4[9]. Tender vegetables such as snap beans and sweet corn can be planted from seed around April 18[10]. Very tender vegetables such as tomatoes and peppers typically wait 2 or more weeks after the last frost, so the earliest start is May 2[11].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (April 18) is March 21 to April 4[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (April 18) is April 4, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, April 18[10]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (April 18), is May 2[11]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Mar 21 May 25 (from transplants)
Cabbage (hardy)[12] Mar 21 Jun 14 (from transplants)
Kohlrabi (hardy)[12] Mar 21 May 10
Lettuce (hardy)[12] Mar 21 May 20
Onions (hardy)[12] Mar 21 Jul 9
Peas (hardy)[12] Mar 21 May 25
Radishes (hardy)[12] Mar 21 Apr 20
Spinach (hardy)[12] Mar 21 Apr 30
Turnips (hardy)[12] Mar 21 May 10
Beets (semi-hardy)[12] Apr 4 Jun 3
Carrots (semi-hardy)[12] Apr 4 Jun 13
Cauliflower (semi-hardy)[12] Apr 4 not listed
Parsnips (semi-hardy)[12] Apr 4 Jun 13
Potatoes (semi-hardy)[12] Apr 4 Aug 7
Swiss chard (semi-hardy)[12] Apr 4 Jun 3
Snap beans (tender)[12] Apr 18 Jun 17
Sweet corn (tender)[12] Apr 18 Jun 17
Cucumbers (tender)[12] Apr 18 Jun 12
Summer squash (tender)[12] Apr 18 Jun 7
Cantaloupe (very tender)[12] May 2 Jul 26
Eggplant (very tender)[12] May 2 Jul 1 (from transplants)
Peppers (very tender)[12] May 2 Jul 11 (from transplants)
Tomatoes (very tender)[12] May 2 Jul 6 (from transplants)
Winter squash (very tender)[12] May 2 Aug 10
Watermelon (very tender)[12] May 2 Jul 26
Spacing, depth and soil temperature (CSU Extension)
Vegetable Min. soil temp Depth Spacing Days to harvest
Broccoli[13] 40°F 1/2 in 18 in 65
Cabbage[13] 40°F 1/2 in 18 in 85
Kohlrabi[13] 40°F 1/2 in 7-9 in 50
Lettuce[13] 35°F 1/4 in 7-9 in 60
Onions[13] 35°F 1/4 in (seed), 1-2 in (sets) 4-6 in 110
Peas[13] 40°F 1 in 4-6 in 65
Radishes[13] 40°F 1/2 in 2-3 in 30
Spinach[13] 40°F 1/2 in 4-6 in 40
Turnips[13] 40°F 1/2 in 4-6 in 50
Beets[13] 40°F 3/4-1 in 4-6 in 60
Carrots[13] 40°F 1/4 in 2-3 in 70
Cauliflower[13] 40°F 1/2 in 18 in –
Parsnips[13] 35°F 1/2 in 5-6 in 70
Potatoes[13] 45°F – – 125
Swiss chard[13] 40°F 1 in 7-9 in 60
Snap beans[13] 55°F 1-1 1/2 in 6 in 60
Sweet corn[13] 50°F 1-1 1/2 in 12 x 30 in or 9 x 36 in 60-90
Cucumbers[13] 60°F 1 in 6 in trellised, 24-36 in untrellised 55
Summer squash[13] 60°F 1-1 1/2 in 36-48 in 50
Cantaloupe[13] 60°F 1-1 1/2 in 36-48 in 85
Eggplant[13] 60°F 1/4 in 18-24 in 60
Peppers[13] 60°F 1/4 in 15-18 in 70
Tomatoes[13] 50°F 1/4 in 24 in trellised 65
Winter squash[13] 60°F 1-1 1/2 in 36-48 in 100
Watermelon[13] 60°F 1-1 1/2 in 36-48 in 85

Hardiness zone

The 2023 USDA map puts the center of Des Moines in zone 5b, which means an average coldest night of -15°F to -10°F over 1991 to 2020[1]. The zone is based on the coldest winter night and not on summer heat or frost dates[14]. By land area, 100% of the city lies in ZIP code areas rated zone 5b[15].

Zone 5b: average annual extreme minimum temperature -15°F to -10°F (1991 to 2020)[1]. Modeled value at the city center: -11.3°F[1].

Share of the city's land area by ZIP code zone: zone 5b 100%[15].

All towns in zone 5b and what zone 5b means

Zone by ZIP code
ZIP code Zone Coldest night range
50317[15] 5b -15 to -10°F
50320[15] 5b -15 to -10°F
50321[15] 5b -15 to -10°F
50315[15] 5b -15 to -10°F
50310[15] 5b -15 to -10°F
50312[15] 5b -15 to -10°F
50313[15] 5b -15 to -10°F
50316[15] 5b -15 to -10°F
50211[15] 5b -15 to -10°F
50309[15] 5b -15 to -10°F
50311[15] 5b -15 to -10°F
50314[15] 5b -15 to -10°F
50047[15] 5b -15 to -10°F
50322[15] 5b -15 to -10°F
50009[15] 5b -15 to -10°F
50319[15] 5b -15 to -10°F

Questions people ask

What growing zone is Des Moines?
The 2023 USDA Plant Hardiness Zone Map puts the center of Des Moines in zone 5b[1].
When is the last frost in Des Moines?
The median last spring frost is April 18, so in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after May 2[2].
When to plant tomatoes in Des Moines?
CSU Extension says tomatoes typically go in 2 or more weeks after the average last frost, which makes May 2 the earliest start here[11]. CSU's guide was written for Colorado[11].
When is the first frost in Des Moines?
The median first fall frost is October 20, so in half of years it comes before that date[3]. In 1 of 10 years it comes before October 4[3].
How long is the growing season in Des Moines?
The growing season is at least 184 days in half of years[4]. It is at least 165 days in 9 of 10 years[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Des Moines, Iowa in zone 5b. Zone 5b means an average annual extreme minimum temperature of -15°F to -10°F over 1991 to 2020. The map's modeled value at the city center is minus 11.3°F. USDA zone map 2023 (PRISM, OSU)
  2. Last spring frost (32°F) at this station: in 9 of 10 years the last frost comes after April 4, in half of years after April 18, and in 1 of 10 years after May 2 (NOAA 1991 to 2020 normals). The median last frost date is April 18. NOAA Climate Normals 1991-2020
  3. First fall frost (32°F) at this station: in 1 of 10 years the first frost comes before October 4, in half of years before October 20, and in 9 of 10 years before November 1 (NOAA 1991 to 2020 normals). The median first frost date is October 20. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 165 days in 9 of 10 years, at least 184 days in half of years, and at least 203 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Des Moines International Airport weather station (USW00014933), 3.5 miles from the center of Des Moines at 957 feet, using 26 years of records from 1991 to 2020. NOAA Climate Normals 1991-2020
  6. Colorado State University Extension's vegetable planting guide (written for Colorado) groups broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips as hardy vegetables, with this rule: as early as 2-4 weeks before the average last... CSU Extension GardenNotes #720
  7. Hard freeze (28°F) at this station: the median last spring date is April 8 and the median first fall date is October 30. NOAA Climate Normals 1991-2020
  8. At this station the low reached 32°F or colder in 100% of years from 1991 to 2020, and 28°F or colder in 100% of years. NOAA Climate Normals 1991-2020
  9. Colorado State University Extension's vegetable planting guide (written for Colorado) groups beets, carrots, cauliflower, parsnips, potatoes, Swiss chard as semi-hardy vegetables, with this rule: as early as 0-2 weeks before the average last spring frost.... CSU Extension GardenNotes #720
  10. Colorado State University Extension's vegetable planting guide (written for Colorado) groups snap beans, sweet corn, cucumbers, summer squash as tender vegetables, with this rule: from seed around the average last spring frost; cucumber and summer squash... CSU Extension GardenNotes #720
  11. Colorado State University Extension's vegetable planting guide (written for Colorado) groups cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon as very tender vegetables, with this rule: typically 2 or more weeks after the average last... CSU Extension GardenNotes #720
  12. GardenFacts calculation: earliest planting date plus CSU days to harvest (table on this page), from the station's median last frost. NOAA Climate Normals 1991-2020
  13. CSU Extension vegetable table: soil temperature, depth, spacing, days to harvest (table on this page). CSU Extension GardenNotes #720
  14. USDA hardiness zones are based on the average annual extreme minimum winter temperature (the coldest night of each winter, averaged over 1991 to 2020 for the 2023 map), not on summer heat or frost dates. Each zone spans 10°F and each half zone (a or b)... USDA Plant Hardiness Zone Map
  15. Des Moines, Iowa overlaps 16 ZIP code areas. By land area, 100% lies in ZIP code areas rated zone 5b. USDA zone map 2023 (PRISM, OSU)

Frost dates are probabilities from 1991 to 2020 weather records at one NOAA station, not a forecast. Any year can be earlier or later. The hardiness zone describes the average coldest winter night, not frost dates or summer heat. Spots inside the city can differ (ZIP table). Planting rules come from Colorado State University Extension's guide, written for Colorado. A local extension office may give dates tuned to the area. Planting and harvest dates marked GardenFacts calculation are simple arithmetic from the facts above, not advice from the source.

Hardiness zone data: USDA Plant Hardiness Zone Map (2023), USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu, accessed October 30, 2026. This is not the official USDA map. Frost data: NOAA NCEI U.S. Climate Normals 1991-2020. Planting rules: Colorado State University Extension.