USDA Hardiness Zone 5a
Frost Dates for 54670 — Wilton, Wisconsin
Averages from Hillsboro, Wi US, the nearest reporting station, 14.6 miles away.
Plant tender crops after May 5, and expect the first autumn freeze around October 4. That leaves about 153 frost-free days.
- Last spring frost
- May 5
- First fall frost
- October 4
- Growing season
- 153 days
- Hardiness zone
- 5a
50% probability
50% probability
frost-free
-20 to -15°F annual low
- First snow
- November 15
- Last snow
- April 6
- Winters with snow
- 100%
- Snow per year
- 41.1"
median, 1991–2020
median, 1991–2020
24 of 24 observed
NOAA normal
When it snows in Wilton, Wisconsin
The first measurable snow (0.1 inch or more) in Wilton, Wisconsin usually arrives around November 15, and the last of the season around April 6. Those are the middle dates across the winters of 1991–2020 at Ontario 3e, Wi US, 8.1 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow.
For a gardener, snow matters less than frost: a light snow on frozen ground changes nothing, while a hard frost on an unprotected bed ends the season. Use the frost dates above for planting and the snow dates for getting hoses drained, mulch down and tender pots indoors.
Planting calendar for 54670
| When | What to do |
|---|---|
| February 24 – March 10 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| March 10 – March 24 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| April 7 – April 21 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| May 5 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by July 12 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by September 20 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| October 4 onward | Plant garlic, mulch beds, lift tender bulbs Garlic wants a cold spell; bare soil loses structure over winter. |
What these dates mean
Wait until after May 5 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Wilton, Wisconsin are past their last freeze. Harvest before October 4, which leaves roughly 153 frost-free days.
ZIP 54670 sits in USDA hardiness zone 5a, meaning the average coldest night of the year falls between -20 to -15°F. Zone decides what survives the winter; frost dates decide when to plant each spring. They are different questions, and a plant can pass one and fail the other.
These are thirty-year NOAA averages for 1991–2020, not a forecast. Any individual year can frost two to three weeks either side of these dates, so check the actual forecast before planting out.