USDA Hardiness Zone 5a
Frost Dates for 52172 — Waukon, Iowa
NOAA 1991–2020 normals from Waukon, IA (1,275 ft), under a mile northeast.
Updated
In Waukon, the last spring frost (32°F) is around May 2 in half of years and has passed by May 16 in nine years out of ten. The first fall frost comes around October 11, as early as September 28 one year in ten, leaving a typical freeze-free season of 161 days (NOAA, Waukon, IA).
- Last spring frost
- May 2
- First fall frost
- October 11
- Growing season
- 161 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 24
- Last snow
- April 2
- Winters with snow
- 100%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
21 of 21 observed
NOAA normal
Frost risk by date in Waukon
Half of springs at Waukon, IA see their last 32°F night by May 2; only one in ten is past it by April 17, and one in ten still has one after May 16. Planting tender crops after May 7 leaves a 30% risk of a frost on them, after May 11 20%, and after May 16 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 11 in half of years, as early as September 28 one year in ten, and holds off past October 24 one year in ten. A hard freeze of 28°F follows 11 days later, around October 22; in spring the one-in-ten date for 28°F is May 6, 10 days before the 32°F one. The freeze-free season lasts 161 days in a typical year, shorter than at 67% of the 132 Iowa stations; it reaches 179 days one year in ten and falls short of 142 one year in ten. On average 160 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 12, and return around October 1. Severe cold of 16°F or below comes every winter, usually between November 19 and March 23.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 29 | May 2 | May 5 | May 9 | May 12 | May 14 | May 18 | May 22 | May 26 |
| 32°F | Apr 17 | Apr 22 | Apr 26 | Apr 30 | May 2 | May 4 | May 7 | May 11 | May 16 |
| 28°F | Apr 6 | Apr 11 | Apr 15 | Apr 18 | Apr 21 | Apr 24 | Apr 28 | May 1 | May 6 |
| 24°F | Mar 27 | Apr 1 | Apr 4 | Apr 6 | Apr 9 | Apr 12 | Apr 16 | Apr 21 | Apr 26 |
| 20°F | Mar 16 | Mar 21 | Mar 26 | Mar 30 | Apr 1 | Apr 3 | Apr 5 | Apr 9 | Apr 16 |
| 16°F | Mar 9 | Mar 13 | Mar 16 | Mar 19 | Mar 23 | Mar 26 | Mar 30 | Apr 1 | Apr 4 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 19 | Sep 23 | Sep 26 | Sep 29 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 14 |
| 32°F | Sep 28 | Oct 1 | Oct 4 | Oct 8 | Oct 11 | Oct 13 | Oct 17 | Oct 20 | Oct 24 |
| 28°F | Oct 7 | Oct 12 | Oct 16 | Oct 19 | Oct 22 | Oct 24 | Oct 27 | Oct 30 | Nov 3 |
| 24°F | Oct 20 | Oct 24 | Oct 27 | Oct 30 | Nov 1 | Nov 3 | Nov 6 | Nov 10 | Nov 15 |
| 20°F | Oct 29 | Nov 2 | Nov 5 | Nov 8 | Nov 10 | Nov 12 | Nov 15 | Nov 19 | Nov 24 |
| 16°F | Nov 5 | Nov 10 | Nov 13 | Nov 15 | Nov 19 | Nov 21 | Nov 25 | Nov 28 | Dec 2 |
Freeze probabilities 1991–2020 at Waukon, 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 52172 →Compare Waukon with another place →
Weather by month in Waukon
July is the warmest month at Waukon, IA, averaging 81°F by day and 62°F at night; January is the coldest at 24°F and 8°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 54% of years.
Warmth for growing adds up to 2,549 growing degree days a year (base 50°F), fewer than at 98% of the 132 Iowa stations. 32% of them (828) have built up by the end of June, and July adds the most, 665.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 24 | 8 | 100% | 31 | 0 |
| Feb | 29 | 12 | 100% | 27 | 0 |
| Mar | 42 | 23 | 100% | 25 | 13 |
| Apr | 56 | 34 | 100% | 12 | 54 |
| May | 68 | 46 | 54% | 2 | 236 |
| Jun | 77 | 58 | 0% | 0 | 525 |
| Jul | 81 | 62 | 0% | 0 | 665 |
| Aug | 79 | 59 | 0% | 0 | 594 |
| Sep | 72 | 51 | 15% | <1 | 352 |
| Oct | 59 | 39 | 97% | 9 | 103 |
| Nov | 43 | 27 | 100% | 23 | 8 |
| Dec | 29 | 15 | 100% | 30 | 0 |
Monthly normals 1991–2020 at Waukon, IA (1,275 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, Postville, IA, 13 miles south of Waukon, has a last frost 1 day earlier (May 1), a first frost 8 days earlier (October 3), a season 8 days shorter.
When it snows in Waukon, Iowa
The first measurable snow (0.1 inch or more) in Waukon usually arrives around November 24, and the last of the season around April 2. Those are the middle dates across the winters of 1991–2020 at Waukon, IA, 0.7 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 30 days after the last snow.
Planting calendar for 52172
| When | What to do |
|---|---|
| February 21 – March 7 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 7 – March 21 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 4 – April 18 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 2 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 19 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 27 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 11 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 52172 is under a mile from Waukon, IA, which stands at 1,275 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 52172 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.