USDA Hardiness Zone 6a
Frost Dates for 51503 — Council Bluffs, Iowa
NOAA 1991–2020 normals from Omaha Eppley Airfield, NE (982 ft), 7 miles northwest.
Updated
In Council Bluffs, the last spring frost (32°F) is around April 18 in half of years and has passed by April 30 in nine years out of ten. The first fall frost comes around October 21, as early as October 6 one year in ten, leaving a typical freeze-free season of 185 days (NOAA, Omaha Eppley Airfield, NE).
- Last spring frost
- April 18
- First fall frost
- October 21
- Growing season
- 185 days
- Hardiness zone
- 6a
50% probability
50% probability
freeze-free, 50%
-10 to -5°F (-23.3 to -20.6°C) coldest night
- First snow
- November 21
- Last snow
- March 25
- Winters with snow
- 100%
- Snow per year
- 27.1"
median, 1991–2020
median, 1991–2020
27 of 27 observed
NOAA normal
Frost risk by date in Council Bluffs
Half of springs at Omaha Eppley Airfield, NE see their last 32°F night by April 18; only one in ten is past it by April 5, and one in ten still has one after April 30. Planting tender crops after April 23 leaves a 30% risk of a frost on them, after April 27 20%, and after April 30 10%. The 12 days between the even-odds date and the one-in-ten date is narrower than at 67% of the 132 Iowa stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 21 in half of years, as early as October 6 one year in ten, and holds off past November 1 one year in ten. A hard freeze of 28°F follows 9 days later, around October 30; in spring the one-in-ten date for 28°F is April 21, 9 days before the 32°F one. The freeze-free season lasts 185 days in a typical year, longer than at 92% of the 132 Iowa stations; it reaches 204 days one year in ten and falls short of 163 one year in ten. On average 135 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 10 days longer, to about April 28, and return around October 10. Severe cold of 16°F or below comes every winter, usually between November 25 and March 10.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 14 | Apr 19 | Apr 23 | Apr 25 | Apr 28 | Apr 30 | May 3 | May 6 | May 11 |
| 32°F | Apr 5 | Apr 9 | Apr 12 | Apr 15 | Apr 18 | Apr 21 | Apr 23 | Apr 27 | Apr 30 |
| 28°F | Mar 24 | Mar 31 | Apr 3 | Apr 5 | Apr 8 | Apr 11 | Apr 14 | Apr 17 | Apr 21 |
| 24°F | Mar 13 | Mar 18 | Mar 22 | Mar 28 | Mar 31 | Apr 2 | Apr 4 | Apr 8 | Apr 13 |
| 20°F | Mar 3 | Mar 8 | Mar 12 | Mar 16 | Mar 20 | Mar 23 | Mar 28 | Mar 31 | Apr 4 |
| 16°F | Feb 22 | Feb 28 | Mar 3 | Mar 6 | Mar 10 | Mar 13 | Mar 16 | Mar 21 | Mar 28 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 27 | Oct 1 | Oct 4 | Oct 8 | Oct 10 | Oct 13 | Oct 16 | Oct 19 | Oct 23 |
| 32°F | Oct 6 | Oct 12 | Oct 15 | Oct 19 | Oct 21 | Oct 23 | Oct 26 | Oct 29 | Nov 1 |
| 28°F | Oct 17 | Oct 22 | Oct 25 | Oct 27 | Oct 30 | Nov 1 | Nov 3 | Nov 6 | Nov 11 |
| 24°F | Oct 26 | Oct 31 | Nov 2 | Nov 5 | Nov 7 | Nov 10 | Nov 13 | Nov 17 | Nov 22 |
| 20°F | Nov 2 | Nov 7 | Nov 10 | Nov 13 | Nov 17 | Nov 20 | Nov 23 | Nov 28 | Dec 3 |
| 16°F | Nov 8 | Nov 14 | Nov 19 | Nov 22 | Nov 25 | Nov 29 | Dec 1 | Dec 6 | Dec 12 |
Freeze probabilities 1991–2020 at Omaha Eppley Airfield, NE, 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 51503 →Compare Council Bluffs with another place →
Weather by month in Council Bluffs
July is the warmest month at Omaha Eppley Airfield, NE, averaging 88°F by day and 68°F at night; January is the coldest at 34°F and 15°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month.
Warmth for growing adds up to 3,787 growing degree days a year (base 50°F), the most of the 132 Iowa stations. 36% of them (1,358) have built up by the end of June, and July adds the most, 869. Precipitation totals 32.1 inches a year, most in May (4.7") and least in January (0.8"); May to September bring 63% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 34 | 15 | 0.8 | 100% | 30 | 0 |
| Feb | 39 | 19 | 1.0 | 100% | 26 | 4 |
| Mar | 52 | 30 | 1.8 | 100% | 20 | 46 |
| Apr | 64 | 41 | 3.2 | 97% | 6 | 163 |
| May | 75 | 53 | 4.7 | 9% | <1 | 428 |
| Jun | 84 | 63 | 4.4 | 0% | 0 | 717 |
| Jul | 88 | 68 | 3.6 | 0% | 0 | 869 |
| Aug | 86 | 66 | 4.6 | 0% | 0 | 797 |
| Sep | 79 | 56 | 3.0 | 4% | <1 | 530 |
| Oct | 66 | 43 | 2.3 | 86% | 4 | 204 |
| Nov | 50 | 30 | 1.5 | 100% | 19 | 29 |
| Dec | 38 | 20 | 1.2 | 100% | 29 | 1 |
Monthly normals 1991–2020 at Omaha Eppley Airfield, NE (982 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, Omaha #1, NE, 14 miles northwest of Council Bluffs and 298 feet higher, has a last frost 2 days earlier (April 16), a first frost 3 days earlier (October 18), a season 2 days shorter.
When it snows in Council Bluffs, Iowa
The first measurable snow (0.1 inch or more) in Council Bluffs usually arrives around November 21, and the last of the season around March 25. Those are the middle dates across the winters of 1991–2020 at Omaha Eppley Airfield, NE, 6.8 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 24 days after the last snow.
Planting calendar for 51503
| 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 29 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 7 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 21 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 51503 is 7 miles from Omaha Eppley Airfield, NE, which stands at 982 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 13 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 51503 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°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.