USDA Hardiness Zone 5a
Frost Dates for 54171 — Sobieski, Wisconsin
NOAA 1991–2020 normals from Green Bay Botanical, WI (694 ft), 13 miles south.
Updated
In Sobieski, the last spring frost (32°F) is around May 7 in half of years and has passed by May 22 in nine years out of ten. The first fall frost comes around October 9, as early as September 23 one year in ten, leaving a typical freeze-free season of 154 days (NOAA, Green Bay Botanical, WI).
- Last spring frost
- May 7
- First fall frost
- October 9
- Growing season
- 154 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 20
- Last snow
- April 10
- Winters with snow
- 100%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
17 of 17 observed
NOAA normal
Frost risk by date in Sobieski
Half of springs at Green Bay Botanical, WI see their last 32°F night by May 7; only one in ten is past it by April 24, and one in ten still has one after May 22. Planting tender crops after May 13 leaves a 30% risk of a frost on them, after May 16 20%, and after May 22 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 9 in half of years, as early as September 23 one year in ten, and holds off past October 25 one year in ten. A hard freeze of 28°F follows 16 days later, around October 25; in spring the one-in-ten date for 28°F is May 12, 10 days before the 32°F one. The freeze-free season lasts 154 days in a typical year, shorter than at 53% of the 182 Wisconsin stations; it reaches 176 days one year in ten and falls short of 134 one year in ten. On average 159 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 19, and return around September 28. Severe cold of 16°F or below comes every winter, usually between November 22 and March 27.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 4 | May 8 | May 13 | May 16 | May 19 | May 21 | May 24 | May 27 | May 31 |
| 32°F | Apr 24 | Apr 29 | May 2 | May 4 | May 7 | May 10 | May 13 | May 16 | May 22 |
| 28°F | Apr 10 | Apr 16 | Apr 20 | Apr 23 | Apr 27 | Apr 30 | May 2 | May 6 | May 12 |
| 24°F | Mar 30 | Apr 3 | Apr 6 | Apr 9 | Apr 12 | Apr 15 | Apr 19 | Apr 22 | Apr 27 |
| 20°F | Mar 18 | Mar 25 | Mar 29 | Apr 1 | Apr 3 | Apr 5 | Apr 8 | Apr 12 | Apr 18 |
| 16°F | Mar 12 | Mar 16 | Mar 19 | Mar 23 | Mar 27 | Mar 30 | Apr 1 | Apr 3 | Apr 8 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 15 | Sep 19 | Sep 22 | Sep 25 | Sep 28 | Sep 30 | Oct 3 | Oct 7 | Oct 12 |
| 32°F | Sep 23 | Sep 28 | Oct 2 | Oct 6 | Oct 9 | Oct 12 | Oct 16 | Oct 20 | Oct 25 |
| 28°F | Oct 5 | Oct 11 | Oct 17 | Oct 22 | Oct 25 | Oct 28 | Oct 31 | Nov 3 | Nov 7 |
| 24°F | Oct 24 | Oct 30 | Nov 1 | Nov 3 | Nov 6 | Nov 8 | Nov 11 | Nov 14 | Nov 19 |
| 20°F | Nov 3 | Nov 6 | Nov 10 | Nov 12 | Nov 15 | Nov 17 | Nov 20 | Nov 22 | Nov 26 |
| 16°F | Nov 8 | Nov 13 | Nov 17 | Nov 19 | Nov 22 | Nov 24 | Nov 26 | Nov 30 | Dec 4 |
Freeze probabilities 1991–2020 at Green Bay Botanical, 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 54171 →Compare Sobieski with another place →
Weather by month in Sobieski
July is the warmest month at Green Bay Botanical, WI, averaging 80°F by day and 59°F at night; January is the coldest at 25°F and 9°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 75% of years.
Warmth for growing adds up to 2,279 growing degree days a year (base 50°F), fewer than at 67% of the 182 Wisconsin stations. 31% of them (714) have built up by the end of June, and July adds the most, 600.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 25 | 9 | 100% | 31 | 0 |
| Feb | 29 | 11 | 100% | 28 | 0 |
| Mar | 40 | 21 | 100% | 26 | 8 |
| Apr | 54 | 33 | 100% | 15 | 45 |
| May | 67 | 44 | 75% | 2 | 209 |
| Jun | 75 | 55 | 0% | 0 | 452 |
| Jul | 80 | 59 | 0% | 0 | 600 |
| Aug | 78 | 57 | 0% | 0 | 550 |
| Sep | 71 | 49 | 25% | <1 | 317 |
| Oct | 58 | 39 | 94% | 9 | 90 |
| Nov | 44 | 27 | 100% | 20 | 8 |
| Dec | 31 | 17 | 100% | 29 | 0 |
Monthly normals 1991–2020 at Green Bay Botanical, WI (694 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, Oconto 4 W, WI, 14 miles northeast of Sobieski, has a last frost 2 days later (May 9), a first frost 3 days earlier (October 6), a season 4 days shorter.
When it snows in Sobieski, Wisconsin
The first measurable snow (0.1 inch or more) in Sobieski usually arrives around November 20, and the last of the season around April 10. Those are the middle dates across the winters of 1991–2020 at Green Bay Botanical, WI, 12.8 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 27 days after the last snow.
Planting calendar for 54171
| When | What to do |
|---|---|
| February 26 – March 12 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 12 – March 26 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 9 – April 23 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 7 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 54171 is 13 miles from Green Bay Botanical, WI, which stands at 694 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 7 other ZIP codes share the station; its figures are presented in full for 54313 (Green Bay). The 2023 USDA Plant Hardiness Zone Map lists ZIP 54171 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.