USDA Hardiness Zone 5b
Frost Dates for 51555 — Missouri Valley, Iowa
NOAA 1991–2020 normals from Logan, IA (990 ft), 8 miles northeast.
Updated
In Missouri Valley, the last spring frost (32°F) is around April 29 in half of years and has passed by May 13 in nine years out of ten. The first fall frost comes around October 8, as early as September 23 one year in ten, leaving a typical freeze-free season of 162 days (NOAA, Logan, IA).
- Last spring frost
- April 29
- First fall frost
- October 8
- Growing season
- 162 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 15
- Last snow
- March 20
- Winters with snow
- 100%
- Snow per year
- 28.7"
median, 1991–2020
median, 1991–2020
21 of 21 observed
NOAA normal
Frost risk by date in Missouri Valley
Half of springs at Logan, IA see their last 32°F night by April 29; only one in ten is past it by April 15, and one in ten still has one after May 13. Planting tender crops after May 4 leaves a 30% risk of a frost on them, after May 7 20%, and after May 13 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 8 in half of years, as early as September 23 one year in ten, and holds off past October 22 one year in ten. A hard freeze of 28°F follows 11 days later, around October 19; in spring the one-in-ten date for 28°F is May 3, 10 days before the 32°F one. The freeze-free season lasts 162 days in a typical year, shorter than at 61% of the 132 Iowa stations; it reaches 180 days one year in ten and falls short of 145 one year in ten. On average 154 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 8 days longer, to about May 7, and return around October 1. Severe cold of 16°F or below comes every winter, usually between November 14 and March 19.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 25 | Apr 30 | May 2 | May 4 | May 7 | May 9 | May 12 | May 15 | May 21 |
| 32°F | Apr 15 | Apr 20 | Apr 24 | Apr 26 | Apr 29 | May 1 | May 4 | May 7 | May 13 |
| 28°F | Apr 6 | Apr 10 | Apr 13 | Apr 16 | Apr 19 | Apr 22 | Apr 25 | Apr 29 | May 3 |
| 24°F | Mar 25 | Mar 31 | Apr 3 | Apr 6 | Apr 9 | Apr 12 | Apr 15 | Apr 19 | Apr 24 |
| 20°F | Mar 12 | Mar 19 | Mar 23 | Mar 28 | Mar 31 | Apr 3 | Apr 6 | Apr 10 | Apr 16 |
| 16°F | Mar 4 | Mar 8 | Mar 12 | Mar 15 | Mar 19 | Mar 23 | Mar 27 | Mar 31 | Apr 5 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 17 | Sep 21 | Sep 25 | Sep 27 | Oct 1 | Oct 2 | Oct 5 | Oct 8 | Oct 12 |
| 32°F | Sep 23 | Sep 29 | Oct 2 | Oct 5 | Oct 8 | Oct 12 | Oct 15 | Oct 18 | Oct 22 |
| 28°F | Oct 3 | Oct 10 | Oct 13 | Oct 16 | Oct 19 | Oct 22 | Oct 24 | Oct 28 | Nov 1 |
| 24°F | Oct 15 | Oct 20 | Oct 23 | Oct 26 | Oct 29 | Oct 31 | Nov 2 | Nov 5 | Nov 10 |
| 20°F | Oct 24 | Oct 28 | Nov 1 | Nov 3 | Nov 5 | Nov 8 | Nov 11 | Nov 14 | Nov 19 |
| 16°F | Nov 1 | Nov 4 | Nov 8 | Nov 11 | Nov 14 | Nov 18 | Nov 21 | Nov 25 | Nov 30 |
Freeze probabilities 1991–2020 at Logan, 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 51555 →Compare Missouri Valley with another place →
Weather by month in Missouri Valley
July is the warmest month at Logan, IA, averaging 86°F by day and 64°F at night; January is the coldest at 31°F and 10°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 44% of years.
Warmth for growing adds up to 3,203 growing degree days a year (base 50°F), more than at 73% of the 132 Iowa stations. 35% of them (1,132) have built up by the end of June, and July adds the most, 770. Precipitation totals 34.5 inches a year, most in June (5.2") and least in January (0.7"); May to September bring 64% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 31 | 10 | 0.7 | 100% | 31 | 0 |
| Feb | 36 | 14 | 1.0 | 100% | 27 | 1 |
| Mar | 49 | 26 | 1.8 | 100% | 24 | 28 |
| Apr | 62 | 36 | 3.4 | 100% | 10 | 110 |
| May | 73 | 49 | 5.0 | 44% | 1 | 355 |
| Jun | 82 | 60 | 5.2 | 0% | 0 | 637 |
| Jul | 86 | 64 | 4.1 | 0% | 0 | 770 |
| Aug | 84 | 61 | 4.3 | 0% | 0 | 696 |
| Sep | 78 | 51 | 3.5 | 24% | 1 | 437 |
| Oct | 65 | 38 | 2.6 | 98% | 9 | 150 |
| Nov | 49 | 25 | 1.5 | 100% | 23 | 18 |
| Dec | 35 | 15 | 1.4 | 100% | 30 | 0 |
Monthly normals 1991–2020 at Logan, IA (990 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, Blair, NE, 12 miles west of Missouri Valley, has a last frost 7 days earlier (April 22), a first frost 9 days later (October 17), a season 15 days longer.
When it snows in Missouri Valley, Iowa
The first measurable snow (0.1 inch or more) in Missouri Valley usually arrives around November 15, and the last of the season around March 20. Those are the middle dates across the winters of 1991–2020 at Logan, IA, 8.2 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 40 days after the last snow.
Planting calendar for 51555
| When | What to do |
|---|---|
| February 18 – March 4 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 4 – March 18 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 1 – April 15 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 29 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 16 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 24 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 8 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 51555 is 8 miles from Logan, IA, which stands at 990 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 51555 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.