Frost dates for 53962Union Center, WI
The average last spring frost in Union Center is May 5 and the average first fall frost is October 4, giving a typical growing season of about 153 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 5
- Average first fall frost
- Oct 4
- Growing season
- 153 days
Safer after May 18 (1-in-10 risk)
Possible by Sep 23 (1-in-10 risk)
Last frost typically in 183 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | May 3 · May 16 · May 30 | Sep 14 · Sep 27 · Oct 8 | 133 days | 100% |
| Frost / freeze (32°F) | Apr 22 · May 5 · May 18 | Sep 23 · Oct 4 · Oct 18 | 153 days | 100% |
| Hard freeze (28°F) | Apr 9 · Apr 23 · May 7 | Oct 2 · Oct 17 · Nov 1 | 176 days | 100% |
Planting calendar for Union Center
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Apr 4 – Jun 10 |
| Tomatoes | Transplant outdoors | May 21 – Jun 14 |
| Peppers | Start seeds indoors | Apr 4 – May 5 |
| Peppers | Transplant outdoors | Jun 4 – Jul 5 |
| Eggplant | Start seeds indoors | Apr 21 – May 20 |
| Eggplant | Transplant outdoors | Jun 4 – Jul 5 |
| Cucumbers | Sow outdoors | Jun 4 – Jun 24 |
| Summer squash | Sow outdoors | May 21 – Jul 5 |
| Winter squash & pumpkins | Sow outdoors | Jun 4 – Jul 5 |
| Snap beans | Sow outdoors | May 21 – Jul 17 |
| Sweet corn | Sow outdoors | May 21 – Jun 14 |
| Watermelon & cantaloupe | Sow outdoors | Jun 4 – Jul 5 |
| Okra | Sow outdoors | May 28 – Jun 20 |
| Peas | Sow outdoors (spring) | Apr 4 – May 20 |
| Potatoes | Plant outdoors (spring) | Apr 4 – Jun 4 |
| Onions | Start seeds indoors (spring) | Feb 21 – Mar 20 |
| Onions | Transplant outdoors (spring) | Apr 21 – May 20 |
| Broccoli | Start seeds indoors (spring) | Mar 17 – Apr 20 |
| Broccoli | Transplant outdoors (spring) | Apr 21 – May 20 |
| Broccoli | Start seeds indoors (fall) | Jun 4 – Jun 14 |
| Broccoli | Transplant outdoors (fall) | Jul 4 – Jul 15 |
| Cabbage | Start seeds indoors (spring) | Mar 7 – Apr 4 |
| Cabbage | Transplant outdoors (spring) | Apr 4 – May 5 |
| Cabbage | Start seeds indoors (fall) | May 25 – Jun 24 |
| Cabbage | Transplant outdoors (fall) | Jun 24 – Jul 25 |
| Leaf lettuce | Sow outdoors (spring) | Apr 4 – Jun 20 |
| Leaf lettuce | Sow outdoors (fall) | Jun 24 – Aug 10 |
| Spinach | Sow outdoors (spring) | Mar 28 – May 11 |
| Spinach | Sow outdoors (fall) | Jul 11 – Aug 15 |
| Radishes | Sow outdoors (spring) | Apr 4 – May 25 |
| Radishes | Sow outdoors (fall) | Jun 24 – Aug 25 |
| Kale | Sow outdoors (spring) | Apr 21 – May 11 |
| Kale | Sow outdoors (fall) | Jun 17 – Jul 25 |
| Carrots | Sow outdoors (spring) | May 5 – Jun 20 |
| Carrots | Sow outdoors (fall) | May 25 – Jul 10 |
| Garlic | Plant outdoors (fall) | Sep 24 – Oct 25 |
Where these dates come from
ZIP code 53962 is matched to the NOAA station Hillsboro, WI, 6.4 km away, at 940 ft elevation (18 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Hillsboro, WI (used) | 940 ft | May 5 | Oct 4 |
| Hillsboro 2Sw, WI | 1,043 ft | May 12 | Sep 29 |
| Mauston 1 Se, WI | 865 ft | May 2 | Oct 7 |
| Reedsburg, WI | 926 ft | May 2 | Oct 7 |
Frost dates near Union Center
- Wonewoc, WI 53968 · last May 5, first Oct 4
- Elroy, WI 53929 · last May 5, first Oct 4
- Kendall, WI 54638 · last May 5, first Oct 4
- Hillsboro, WI 54634 · last May 5, first Oct 4
- La Valle, WI 53941 · last May 2, first Oct 7
- Mauston, WI 53948 · last May 2, first Oct 7
- Cazenovia, WI 53924 · last May 5, first Oct 4
- Hustler, WI 54637 · last May 1, first Oct 3
Frequently asked questions
- When is the last frost in Union Center, WI?
- For ZIP code 53962, the average last spring frost (32°F) is May 5, based on NOAA 1991-2020 climate normals for the Hillsboro, WI weather station. There is a 1-in-10 chance of a frost after May 18.
- When is the first frost in Union Center, WI?
- The average first fall frost (32°F) is October 4. There is a 1-in-10 chance of frost by September 23, so tender plants are at risk from that point on.
- How long is the growing season in 53962?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 153 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.