USDA Hardiness Zone 4b
Frost Dates for 54634 — Hillsboro, Wisconsin
NOAA 1991–2020 normals from Hillsboro 2SW, WI (1,043 ft), 2 miles northeast.
Updated
In Hillsboro, the last spring frost (32°F) is around May 12 in half of years and has passed by May 26 in nine years out of ten. The first fall frost comes around September 29, as early as September 17 one year in ten, leaving a typical freeze-free season of 138 days (NOAA, Hillsboro 2SW, WI).
- Last spring frost
- May 12
- First fall frost
- September 29
- Growing season
- 138 days
- Hardiness zone
- 4b
50% probability
50% probability
freeze-free, 50%
-25 to -20°F (-31.7 to -28.9°C) coldest night
- First snow
- November 26
- Last snow
- April 10
- Winters with snow
- 100%
- Snow per year
- 38.7"
median, 1991–2020
median, 1991–2020
19 of 19 observed
NOAA normal
Frost risk by date in Hillsboro
Half of springs at Hillsboro 2SW, WI see their last 32°F night by May 12; only one in ten is past it by April 28, and one in ten still has one after May 26. Planting tender crops after May 18 leaves a 30% risk of a frost on them, after May 22 20%, and after May 26 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 58% of the 182 Wisconsin stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 29 in half of years, as early as September 17 one year in ten, and holds off past October 10 one year in ten. A hard freeze of 28°F follows 9 days later, around October 8; in spring the one-in-ten date for 28°F is May 15, 11 days before the 32°F one. The freeze-free season lasts 138 days in a typical year, shorter than at 88% of the 182 Wisconsin stations; it reaches 158 days one year in ten and falls short of 121 one year in ten. On average 181 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 11 days longer, to about May 23, and return around September 20. Severe cold of 16°F or below comes every winter, usually between November 12 and April 1.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 10 | May 14 | May 17 | May 20 | May 23 | May 26 | May 29 | Jun 1 | Jun 5 |
| 32°F | Apr 28 | May 3 | May 6 | May 9 | May 12 | May 15 | May 18 | May 22 | May 26 |
| 28°F | Apr 18 | Apr 22 | Apr 26 | Apr 30 | May 1 | May 4 | May 7 | May 10 | May 15 |
| 24°F | Apr 7 | Apr 11 | Apr 15 | Apr 18 | Apr 21 | Apr 24 | Apr 28 | May 1 | May 5 |
| 20°F | Mar 28 | Apr 2 | Apr 4 | Apr 7 | Apr 10 | Apr 13 | Apr 17 | Apr 20 | Apr 26 |
| 16°F | Mar 15 | Mar 21 | Mar 25 | Mar 30 | Apr 1 | Apr 3 | Apr 6 | Apr 9 | Apr 16 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 6 | Sep 11 | Sep 15 | Sep 18 | Sep 20 | Sep 23 | Sep 25 | Sep 28 | Oct 2 |
| 32°F | Sep 17 | Sep 21 | Sep 24 | Sep 26 | Sep 29 | Oct 1 | Oct 4 | Oct 6 | Oct 10 |
| 28°F | Sep 25 | Sep 30 | Oct 3 | Oct 5 | Oct 8 | Oct 10 | Oct 13 | Oct 16 | Oct 21 |
| 24°F | Oct 6 | Oct 11 | Oct 15 | Oct 18 | Oct 20 | Oct 22 | Oct 25 | Oct 28 | Nov 1 |
| 20°F | Oct 18 | Oct 23 | Oct 26 | Oct 29 | Oct 31 | Nov 2 | Nov 5 | Nov 9 | Nov 16 |
| 16°F | Oct 31 | Nov 2 | Nov 6 | Nov 9 | Nov 12 | Nov 16 | Nov 19 | Nov 23 | Nov 28 |
Freeze probabilities 1991–2020 at Hillsboro 2SW, 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 54634 →Compare Hillsboro with another place →
Compared with the next station
The nearest other station, Hillsboro, WI, 5 miles northeast of Hillsboro, has a last frost 7 days earlier (May 5), a first frost 5 days later (October 4), a season 15 days longer.
When it snows in Hillsboro, Wisconsin
The first measurable snow (0.1 inch or more) in Hillsboro usually arrives around November 26, and the last of the season around April 10. Those are the middle dates across the winters of 1991–2020 at Hillsboro, WI, 4.8 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 32 days after the last snow.
Planting calendar for 54634
| When | What to do |
|---|---|
| March 3 – March 17 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 17 – March 31 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 14 – April 28 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 12 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 7 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 15 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 29 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 54634 is 2 miles from Hillsboro 2SW, WI, which stands at 1,043 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 54634 in zone 4b, the band where the coldest night of the year averaged -25 to -20°F (-31.7 to -28.9°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.