USDA Hardiness Zone 5a
Frost Dates for 50247 — State Center, Iowa
NOAA 1991–2020 normals from Colo, IA (1,000 ft), 8 miles west.
Updated
In State Center, the last spring frost (32°F) is around April 24 in half of years and has passed by May 7 in nine years out of ten. The first fall frost comes around October 12, as early as September 28 one year in ten, leaving a typical freeze-free season of 170 days (NOAA, Colo, IA).
- Last spring frost
- April 24
- First fall frost
- October 12
- Growing season
- 170 days
- Hardiness zone
- 5a
50% probability
50% probability
freeze-free, 50%
-20 to -15°F (-28.9 to -26.1°C) coldest night
- First snow
- November 27
- Last snow
- March 26
- Winters with snow
- 100%
- Snow per year
- 30.6"
median, 1991–2020
median, 1991–2020
18 of 18 observed
NOAA normal
Frost risk by date in State Center
Half of springs at Colo, IA see their last 32°F night by April 24; only one in ten is past it by April 9, and one in ten still has one after May 7. Planting tender crops after April 30 leaves a 30% risk of a frost on them, after May 3 20%, and after May 7 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 42% of the 132 Iowa stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 12 in half of years, as early as September 28 one year in ten, and holds off past October 26 one year in ten. A hard freeze of 28°F follows 11 days later, around October 23; in spring the one-in-ten date for 28°F is April 29, 8 days before the 32°F one. The freeze-free season lasts 170 days in a typical year, longer than at 69% of the 132 Iowa stations; it reaches 190 days one year in ten and falls short of 150 one year in ten. On average 151 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 May 4, and return around October 1. Severe cold of 16°F or below comes every winter, usually between November 19 and March 16.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 20 | Apr 25 | Apr 30 | May 2 | May 4 | May 6 | May 8 | May 11 | May 15 |
| 32°F | Apr 9 | Apr 14 | Apr 17 | Apr 21 | Apr 24 | Apr 27 | Apr 30 | May 3 | May 7 |
| 28°F | Apr 1 | Apr 5 | Apr 8 | Apr 11 | Apr 14 | Apr 17 | Apr 20 | Apr 24 | Apr 29 |
| 24°F | Mar 19 | Mar 26 | Mar 31 | Apr 2 | Apr 4 | Apr 7 | Apr 10 | Apr 15 | Apr 21 |
| 20°F | Mar 9 | Mar 14 | Mar 19 | Mar 22 | Mar 26 | Mar 31 | Apr 2 | Apr 6 | Apr 11 |
| 16°F | Mar 2 | Mar 6 | Mar 10 | Mar 13 | Mar 16 | Mar 19 | Mar 23 | Mar 27 | Apr 1 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 19 | Sep 24 | Sep 27 | Sep 29 | Oct 1 | Oct 4 | Oct 8 | Oct 11 | Oct 16 |
| 32°F | Sep 28 | Oct 1 | Oct 5 | Oct 9 | Oct 12 | Oct 15 | Oct 18 | Oct 21 | Oct 26 |
| 28°F | Oct 9 | Oct 14 | Oct 17 | Oct 20 | Oct 23 | Oct 25 | Oct 28 | Oct 31 | Nov 4 |
| 24°F | Oct 20 | Oct 24 | Oct 27 | Oct 30 | Nov 1 | Nov 3 | Nov 6 | Nov 9 | Nov 15 |
| 20°F | Oct 27 | Nov 1 | Nov 3 | Nov 6 | Nov 9 | Nov 12 | Nov 16 | Nov 21 | Nov 27 |
| 16°F | Nov 4 | Nov 8 | Nov 12 | Nov 16 | Nov 19 | Nov 23 | Nov 27 | Dec 1 | Dec 5 |
Freeze probabilities 1991–2020 at Colo, 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 50247 →Compare State Center with another place →
Weather by month in State Center
July is the warmest month at Colo, IA, averaging 83°F by day and 63°F at night; January is the coldest at 27°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 29% of years.
Warmth for growing adds up to 2,971 growing degree days a year (base 50°F), fewer than at 55% of the 132 Iowa stations. 35% of them (1,032) have built up by the end of June, and July adds the most, 718. Precipitation totals 36.4 inches a year, most in June (5.8") and least in January (1.0"); May to September bring 62% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 27 | 10 | 1.0 | 100% | 31 | 0 |
| Feb | 31 | 14 | 1.2 | 100% | 26 | 1 |
| Mar | 45 | 26 | 2.0 | 100% | 24 | 19 |
| Apr | 59 | 37 | 3.5 | 99% | 9 | 94 |
| May | 70 | 49 | 4.8 | 29% | 1 | 319 |
| Jun | 80 | 60 | 5.8 | 0% | 0 | 600 |
| Jul | 83 | 63 | 4.3 | 0% | 0 | 718 |
| Aug | 81 | 61 | 4.2 | 0% | 0 | 655 |
| Sep | 75 | 52 | 3.4 | 16% | 1 | 410 |
| Oct | 62 | 39 | 2.7 | 97% | 8 | 135 |
| Nov | 46 | 27 | 2.0 | 100% | 22 | 20 |
| Dec | 32 | 16 | 1.5 | 100% | 30 | 1 |
Monthly normals 1991–2020 at Colo, IA (1,000 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, Marshalltown, IA, 13 miles east of State Center, has a last frost 4 days later (April 28), a first frost 5 days earlier (October 7), a season 8 days shorter.
When it snows in State Center, Iowa
The first measurable snow (0.1 inch or more) in State Center usually arrives around November 27, and the last of the season around March 26. Those are the middle dates across the winters of 1991–2020 at Colo, IA, 7.7 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 29 days after the last snow.
Planting calendar for 50247
| When | What to do |
|---|---|
| February 13 – February 27 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 27 – March 13 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 27 – April 10 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 24 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 20 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 28 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 12 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 50247 is 8 miles from Colo, IA, which stands at 1,000 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 50201 (Nevada). The 2023 USDA Plant Hardiness Zone Map lists ZIP 50247 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°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.