USDA Hardiness Zone 5b
Frost Dates for 50320 — Des Moines, Iowa
NOAA 1991–2020 normals from Des Moines International Airport, IA (957 ft), 4 miles west.
Updated
In Des Moines, the last spring frost (32°F) is around April 18 in half of years and has passed by May 2 in nine years out of ten. The first fall frost comes around October 20, as early as October 4 one year in ten, leaving a typical freeze-free season of 184 days (NOAA, Des Moines International Airport, IA).
- Last spring frost
- April 18
- First fall frost
- October 20
- Growing season
- 184 days
- Hardiness zone
- 5b
50% probability
50% probability
freeze-free, 50%
-15 to -10°F (-26.1 to -23.3°C) coldest night
- First snow
- November 11
- Last snow
- April 7
- Winters with snow
- 100%
- Snow per year
- 36.5"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Des Moines
Half of springs at Des Moines International Airport, IA see their last 32°F night by April 18; only one in ten is past it by April 4, and one in ten still has one after May 2. Planting tender crops after April 24 leaves a 30% risk of a frost on them, after April 28 20%, and after May 2 10%. The 14 days between the even-odds date and the one-in-ten date is wider than at 58% of the 132 Iowa stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 20 in half of years, as early as October 4 one year in ten, and holds off past November 1 one year in ten. A hard freeze of 28°F follows 10 days later, around October 30; in spring the one-in-ten date for 28°F is April 22, 10 days before the 32°F one. The freeze-free season lasts 184 days in a typical year, longer than at 89% of the 132 Iowa stations; it reaches 203 days one year in ten and falls short of 165 one year in ten. On average 128 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 11 days longer, to about April 29, and return around October 9. Severe cold of 16°F or below comes every winter, usually between November 24 and March 11.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 15 | Apr 19 | Apr 23 | Apr 26 | Apr 29 | May 1 | May 3 | May 6 | May 10 |
| 32°F | Apr 4 | Apr 9 | Apr 12 | Apr 14 | Apr 18 | Apr 21 | Apr 24 | Apr 28 | May 2 |
| 28°F | Mar 25 | Mar 31 | Apr 3 | Apr 6 | Apr 8 | Apr 10 | Apr 13 | Apr 17 | Apr 22 |
| 24°F | Mar 12 | Mar 19 | Mar 23 | Mar 28 | Mar 31 | Apr 2 | Apr 5 | Apr 8 | Apr 13 |
| 20°F | Mar 3 | Mar 9 | Mar 12 | Mar 17 | Mar 20 | Mar 24 | Mar 27 | Mar 31 | Apr 3 |
| 16°F | Feb 24 | Mar 1 | Mar 5 | Mar 8 | Mar 11 | Mar 14 | Mar 18 | Mar 22 | Mar 29 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 25 | Sep 29 | Oct 3 | Oct 6 | Oct 9 | Oct 12 | Oct 15 | Oct 18 | Oct 22 |
| 32°F | Oct 4 | Oct 10 | Oct 14 | Oct 17 | Oct 20 | Oct 23 | Oct 25 | Oct 28 | Nov 1 |
| 28°F | Oct 16 | Oct 21 | Oct 25 | Oct 27 | Oct 30 | Nov 1 | Nov 2 | Nov 6 | Nov 11 |
| 24°F | Oct 25 | Oct 30 | Nov 1 | Nov 3 | Nov 6 | Nov 9 | Nov 12 | Nov 16 | Nov 21 |
| 20°F | Nov 1 | Nov 4 | Nov 8 | Nov 11 | Nov 14 | Nov 17 | Nov 21 | Nov 26 | Dec 2 |
| 16°F | Nov 7 | Nov 13 | Nov 16 | Nov 20 | Nov 24 | Nov 27 | Dec 1 | Dec 4 | Dec 10 |
Freeze probabilities 1991–2020 at Des Moines International Airport, IA, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 50320 →Compare Des Moines with another place →
Weather by month in Des Moines
July is the warmest month at Des Moines International Airport, IA, averaging 86°F by day and 66°F at night; January is the coldest at 31°F and 14°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 13% of years.
Warmth for growing adds up to 3,476 growing degree days a year (base 50°F), more than at 94% of the 132 Iowa stations. 36% of them (1,234) have built up by the end of June, and July adds the most, 806. Precipitation totals 36.6 inches a year, most in June (5.3") and least in January (1.1"); May to September bring 59% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 31 | 14 | 1.1 | 100% | 30 | 0 |
| Feb | 36 | 18 | 1.3 | 100% | 25 | 3 |
| Mar | 49 | 30 | 2.2 | 100% | 19 | 38 |
| Apr | 62 | 41 | 4.0 | 95% | 6 | 139 |
| May | 72 | 52 | 5.2 | 13% | <1 | 390 |
| Jun | 82 | 62 | 5.3 | 0% | 0 | 664 |
| Jul | 86 | 66 | 3.8 | 0% | 0 | 806 |
| Aug | 84 | 64 | 4.2 | 0% | 0 | 741 |
| Sep | 77 | 55 | 3.2 | 6% | 0 | 487 |
| Oct | 63 | 43 | 2.8 | 89% | 4 | 180 |
| Nov | 48 | 30 | 1.9 | 100% | 17 | 27 |
| Dec | 36 | 20 | 1.6 | 100% | 27 | 1 |
Monthly normals 1991–2020 at Des Moines International Airport, IA (957 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Indianola 2W, IA, 12 miles south of Des Moines, has a last frost 6 days later (April 24), a first frost 8 days earlier (October 12), a season 16 days shorter.
When it snows in Des Moines, Iowa
The first measurable snow (0.1 inch or more) in Des Moines usually arrives around November 11, and the last of the season around April 7. Those are the middle dates across the winters of 1991–2020 at Des Moines International Airport, IA, 3.7 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 11 days after the last snow.
Planting calendar for 50320
| When | What to do |
|---|---|
| February 7 – February 21 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 21 – March 7 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 21 – April 4 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 18 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 28 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 6 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 20 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 50320 is 4 miles from Des Moines International Airport, IA, which stands at 957 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 18 other ZIP codes share the station; its figures are presented in full for 50266 (West Des Moines). The 2023 USDA Plant Hardiness Zone Map lists ZIP 50320 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.