USDA Hardiness Zone 5a
Frost Dates for 53035 — Iron Ridge, Wisconsin
NOAA 1991–2020 normals from Hustisford Wwtp, WI (864 ft), 5 miles southwest.
Updated
In Iron Ridge, the last spring frost (32°F) is around April 28 in half of years and has passed by May 13 in nine years out of ten. The first fall frost comes around October 10, as early as September 26 one year in ten, leaving a typical freeze-free season of 164 days (NOAA, Hustisford Wwtp, WI).
- Last spring frost
- April 28
- First fall frost
- October 10
- Growing season
- 164 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 22
- Last snow
- March 30
- Winters with snow
- 100%
- Snow per year
- 40.8"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Iron Ridge
Half of springs at Hustisford Wwtp, WI see their last 32°F night by April 28; 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 3 leaves a 30% risk of a frost on them, after May 8 20%, and after May 13 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 30% of the 182 Wisconsin stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 10 in half of years, as early as September 26 one year in ten, and holds off past October 24 one year in ten. A hard freeze of 28°F follows 12 days later, around October 22; in spring the one-in-ten date for 28°F is April 30, 13 days before the 32°F one. The freeze-free season lasts 164 days in a typical year, longer than at 71% of the 182 Wisconsin stations; it reaches 183 days one year in ten and falls short of 143 one year in ten. On average 149 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 12 days longer, to about May 10, and return around October 1. Severe cold of 16°F or below comes every winter, usually between November 23 and March 20.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 26 | May 1 | May 4 | May 7 | May 10 | May 12 | May 16 | May 20 | May 26 |
| 32°F | Apr 14 | Apr 19 | Apr 23 | Apr 25 | Apr 28 | Apr 30 | May 3 | May 8 | May 13 |
| 28°F | Apr 3 | Apr 6 | Apr 10 | Apr 13 | Apr 16 | Apr 19 | Apr 22 | Apr 26 | Apr 30 |
| 24°F | Mar 22 | Mar 29 | Apr 1 | Apr 3 | Apr 5 | Apr 7 | Apr 10 | Apr 14 | Apr 18 |
| 20°F | Mar 13 | Mar 18 | Mar 21 | Mar 25 | Mar 28 | Mar 31 | Apr 2 | Apr 5 | Apr 10 |
| 16°F | Mar 7 | Mar 11 | Mar 15 | Mar 18 | Mar 20 | Mar 23 | Mar 26 | Mar 29 | Apr 2 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 18 | Sep 22 | Sep 25 | Sep 28 | Oct 1 | Oct 3 | Oct 5 | Oct 8 | Oct 12 |
| 32°F | Sep 26 | Sep 30 | Oct 4 | Oct 7 | Oct 10 | Oct 12 | Oct 15 | Oct 18 | Oct 24 |
| 28°F | Oct 6 | Oct 11 | Oct 15 | Oct 18 | Oct 22 | Oct 24 | Oct 27 | Oct 31 | Nov 5 |
| 24°F | Oct 18 | Oct 24 | Oct 28 | Oct 30 | Nov 1 | Nov 4 | Nov 8 | Nov 11 | Nov 17 |
| 20°F | Oct 30 | Nov 2 | Nov 6 | Nov 10 | Nov 14 | Nov 17 | Nov 21 | Nov 25 | Nov 30 |
| 16°F | Nov 6 | Nov 12 | Nov 17 | Nov 20 | Nov 23 | Nov 26 | Nov 29 | Dec 2 | Dec 8 |
Freeze probabilities 1991–2020 at Hustisford Wwtp, WI, 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 53035 →Compare Iron Ridge with another place →
Weather by month in Iron Ridge
July is the warmest month at Hustisford Wwtp, WI, averaging 82°F by day and 61°F at night; January is the coldest at 26°F and 11°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 40% of years.
Warmth for growing adds up to 2,584 growing degree days a year (base 50°F), more than at 68% of the 182 Wisconsin stations. 33% of them (863) have built up by the end of June, and July adds the most, 663.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 26 | 11 | 100% | 29 | 0 |
| Feb | 30 | 13 | 100% | 27 | 1 |
| Mar | 42 | 24 | 100% | 25 | 12 |
| Apr | 56 | 36 | 100% | 10 | 63 |
| May | 68 | 47 | 40% | 1 | 260 |
| Jun | 78 | 57 | 0% | 0 | 527 |
| Jul | 82 | 61 | 0% | 0 | 663 |
| Aug | 80 | 58 | 0% | 0 | 590 |
| Sep | 73 | 50 | 21% | <1 | 359 |
| Oct | 59 | 39 | 97% | 8 | 100 |
| Nov | 44 | 28 | 100% | 20 | 9 |
| Dec | 32 | 17 | 100% | 29 | 1 |
Monthly normals 1991–2020 at Hustisford Wwtp, WI (864 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, Horicon Wwtp, WI, 6 miles northwest of Iron Ridge, has a last frost 3 days later (May 1), the same first-frost date, a season 6 days shorter.
When it snows in Iron Ridge, Wisconsin
The first measurable snow (0.1 inch or more) in Iron Ridge usually arrives around November 22, and the last of the season around March 30. Those are the middle dates across the winters of 1991–2020 at Horicon Wwtp, WI, 5.6 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 53035
| When | What to do |
|---|---|
| February 17 – March 3 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 3 – March 17 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 31 – April 14 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 28 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 18 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 26 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 10 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 53035 is 5 miles from Hustisford Wwtp, WI, which stands at 864 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 53035 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.
Frost dates across Wisconsin →
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.