USDA Hardiness Zone 5a
Frost Dates for 50629 — Fairbank, Iowa
NOAA 1991–2020 normals from Oelwein 2 S, IA (1,010 ft), 8 miles east.
Updated
In Fairbank, the last spring frost (32°F) is around April 30 in half of years and has passed by May 13 in nine years out of ten. The first fall frost comes around October 9, as early as September 26 one year in ten, leaving a typical freeze-free season of 163 days (NOAA, Oelwein 2 S, IA).
- Last spring frost
- April 30
- First fall frost
- October 9
- Growing season
- 163 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 13
- Last snow
- March 17
- Winters with snow
- 100%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
15 of 15 observed
NOAA normal
Frost risk by date in Fairbank
Half of springs at Oelwein 2 S, IA see their last 32°F night by April 30; only one in ten is past it by April 14, and one in ten still has one after May 13. Planting tender crops after May 5 leaves a 30% risk of a frost on them, after May 9 20%, and after May 13 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 9 in half of years, as early as September 26 one year in ten, and holds off past October 20 one year in ten. A hard freeze of 28°F follows 10 days later, around October 19; in spring the one-in-ten date for 28°F is May 4, 9 days before the 32°F one. The freeze-free season lasts 163 days in a typical year, shorter than at 58% of the 132 Iowa stations; it reaches 180 days one year in ten and falls short of 143 one year in ten. On average 153 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 8, 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 3 | May 6 | May 8 | May 11 | May 14 | May 17 | May 22 |
| 32°F | Apr 14 | Apr 18 | Apr 23 | Apr 26 | Apr 30 | May 2 | May 5 | May 9 | May 13 |
| 28°F | Apr 3 | Apr 8 | Apr 11 | Apr 15 | Apr 19 | Apr 22 | Apr 25 | Apr 30 | May 4 |
| 24°F | Mar 22 | Mar 29 | Apr 1 | Apr 3 | Apr 6 | Apr 9 | Apr 12 | Apr 17 | Apr 23 |
| 20°F | Mar 12 | Mar 17 | Mar 21 | Mar 25 | Mar 29 | Mar 31 | Apr 3 | Apr 6 | Apr 13 |
| 16°F | Mar 4 | Mar 9 | Mar 13 | Mar 15 | Mar 19 | Mar 22 | Mar 25 | Mar 29 | Apr 2 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 17 | Sep 22 | Sep 26 | Sep 28 | Oct 1 | Oct 3 | Oct 5 | Oct 9 | Oct 13 |
| 32°F | Sep 26 | Oct 1 | Oct 4 | Oct 7 | Oct 9 | Oct 12 | Oct 14 | Oct 17 | Oct 20 |
| 28°F | Oct 6 | Oct 10 | Oct 14 | Oct 17 | Oct 19 | Oct 21 | Oct 23 | Oct 26 | Oct 29 |
| 24°F | Oct 15 | Oct 20 | Oct 23 | Oct 25 | Oct 27 | Oct 29 | Nov 1 | Nov 4 | Nov 9 |
| 20°F | Oct 24 | Oct 28 | Oct 31 | Nov 2 | Nov 5 | Nov 8 | Nov 11 | Nov 14 | Nov 20 |
| 16°F | Nov 2 | Nov 5 | Nov 8 | Nov 11 | Nov 14 | Nov 17 | Nov 21 | Nov 24 | Nov 29 |
Freeze probabilities 1991–2020 at Oelwein 2 S, 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 50629 →Compare Fairbank with another place →
Weather by month in Fairbank
July is the warmest month at Oelwein 2 S, IA, averaging 82°F by day and 62°F at night; January is the coldest at 26°F and 7°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 45% of years.
Warmth for growing adds up to 2,750 growing degree days a year (base 50°F), fewer than at 83% of the 132 Iowa stations. 35% of them (951) have built up by the end of June, and July adds the most, 677.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 26 | 7 | 100% | 31 | 0 |
| Feb | 29 | 10 | 100% | 26 | 0 |
| Mar | 43 | 24 | 100% | 25 | 13 |
| Apr | 58 | 37 | 99% | 10 | 76 |
| May | 69 | 48 | 45% | 1 | 289 |
| Jun | 79 | 59 | 0% | 0 | 574 |
| Jul | 82 | 62 | 0% | 0 | 677 |
| Aug | 79 | 60 | 0% | 0 | 612 |
| Sep | 74 | 51 | 20% | 1 | 386 |
| Oct | 60 | 38 | 99% | 8 | 112 |
| Nov | 44 | 25 | 100% | 22 | 11 |
| Dec | 31 | 15 | 100% | 29 | 1 |
Monthly normals 1991–2020 at Oelwein 2 S, IA (1,010 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, Oelwein 1E, IA, 10 miles east of Fairbank and 155 feet higher, has a last frost 3 days earlier (April 27), a first frost 4 days later (October 13), a season 6 days longer.
When it snows in Fairbank, Iowa
The first measurable snow (0.1 inch or more) in Fairbank usually arrives around November 13, and the last of the season around March 17. Those are the middle dates across the winters of 1991–2020 at Oelwein 2 S, IA, 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 44 days after the last snow.
Planting calendar for 50629
| When | What to do |
|---|---|
| February 19 – March 5 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 5 – March 19 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 2 – April 16 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 30 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 17 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 25 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 9 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 50629 is 8 miles from Oelwein 2 S, IA, which stands at 1,010 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 50629 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.