Grafton, WI frost dates
Last spring frostApr 23median date
First fall frostOct 24median date
Growing season184 daysfrost-free
Hardiness zone6aZone 6a
How Grafton compares
- In 8 years out of 10, the last spring frost in Grafton falls between April 10 and May 9, a 29-day window. The first fall frost falls between October 8 and November 5.
- The median last frost is 12 days earlier than the Wisconsin median of May 5.
- Its 184-day growing season is among the longest of the 749 Wisconsin places with a regular frost season.
- The last frost is 6 days earlier than the zone 6a median of Apr 29. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 6a chart.
- The weather station records an average of 134 nights a year at or below 32°F.
- Compared with Milwaukee, WI, 30 km away, the last frost here is 3 days earlier than there and the growing season is 5 days longer.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 10 |
| 50% (median) | April 23 |
| 10% (safe for tender plants) | May 9 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 8 |
| 50% (median) | October 24 |
| 90% (late) | November 5 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Grafton, WI
Grafton, WI frost dates — last frost Apr 23, first frost Oct 24, zone 6a. whenisthelastfrost.com
Crop
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Start indoors: Jan 29 to Feb 12Transplant outside: Mar 26 to Apr 9
Start indoors: Feb 12 to Feb 26Transplant outside: May 7 to May 21
Start indoors: Feb 12 to Feb 26Transplant outside: May 7 to May 21
Start indoors: Feb 26 to Mar 12Transplant outside: Apr 30 to May 14
Start indoors: Feb 26 to Mar 12Transplant outside: Apr 2 to Apr 16Sow outdoors: Mar 26 to Apr 30Plant for fall: Aug 29 to Sep 26
Start indoors: Feb 26 to Mar 12Transplant outside: Mar 26 to Apr 9Sow outdoors: Mar 26 to Apr 9Plant for fall: Aug 15 to Sep 5
Start indoors: Feb 26 to Mar 12Transplant outside: Apr 9 to Apr 23Plant for fall: Jul 18 to Aug 8
Start indoors: Feb 26 to Mar 12Transplant outside: Apr 2 to Apr 16Plant for fall: Jul 18 to Aug 8
Start indoors: Feb 26 to Mar 12Transplant outside: Apr 9 to Apr 23Plant for fall: Jul 18 to Aug 8
Start indoors: Mar 12 to Mar 26Transplant outside: May 14 to May 28Sow outdoors: May 14 to May 28
Start indoors: Mar 12 to Mar 26Transplant outside: Apr 30 to May 14
Sow outdoors: Mar 12 to Apr 2Plant for fall: Aug 1 to Aug 22
Sow outdoors: Mar 12 to Apr 2Plant for fall: Aug 29 to Sep 19
Sow outdoors: Mar 19 to Apr 30Plant for fall: Sep 12 to Oct 3
Start indoors: Mar 26 to Apr 2Transplant outside: May 7 to May 14Sow outdoors: Apr 30 to May 14Plant for fall: Aug 8 to Aug 22
Start indoors: Mar 26 to Apr 2Sow outdoors: Apr 30 to May 14Plant for fall: Aug 15 to Aug 29
Start indoors: Mar 26 to Apr 2Sow outdoors: Apr 30 to May 14
Start indoors: Mar 26 to Apr 2Transplant outside: May 7 to May 21
Sow outdoors: Apr 2 to Apr 30Plant for fall: Aug 1 to Aug 15
Sow outdoors: Apr 2 to Apr 30Plant for fall: Aug 15 to Aug 29
Sow outdoors: Apr 2 to Apr 23
Sow outdoors: Apr 9 to May 7Plant for fall: Aug 15 to Aug 29
Sow outdoors: Apr 9 to Apr 30Plant for fall: Aug 29 to Sep 19
Sow outdoors: Apr 30 to May 21Plant for fall: Aug 8 to Aug 22
Sow outdoors: Apr 30 to May 14
Transplant outside: May 7 to May 28
Plant for fall: Oct 10 to Nov 14
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Grafton, WI
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Jan 29 – Feb 12 | Mar 26 – Apr 9 | — | — |
| Peppers | Feb 12 – Feb 26 | May 7 – May 21 | — | — |
| Eggplant | Feb 12 – Feb 26 | May 7 – May 21 | — | — |
| Tomatoes | Feb 26 – Mar 12 | Apr 30 – May 14 | — | — |
| Lettuce | Feb 26 – Mar 12 | Apr 2 – Apr 16 | Mar 26 – Apr 30 | Aug 29 – Sep 26 |
| Kale | Feb 26 – Mar 12 | Mar 26 – Apr 9 | Mar 26 – Apr 9 | Aug 15 – Sep 5 |
| Broccoli | Feb 26 – Mar 12 | Apr 9 – Apr 23 | — | Jul 18 – Aug 8 |
| Cabbage | Feb 26 – Mar 12 | Apr 2 – Apr 16 | — | Jul 18 – Aug 8 |
| Cauliflower | Feb 26 – Mar 12 | Apr 9 – Apr 23 | — | Jul 18 – Aug 8 |
| Okra | Mar 12 – Mar 26 | May 14 – May 28 | May 14 – May 28 | — |
| Basil | Mar 12 – Mar 26 | Apr 30 – May 14 | — | — |
| Peas | — | — | Mar 12 – Apr 2 | Aug 1 – Aug 22 |
| Spinach | — | — | Mar 12 – Apr 2 | Aug 29 – Sep 19 |
| Radishes | — | — | Mar 19 – Apr 30 | Sep 12 – Oct 3 |
| Cucumbers | Mar 26 – Apr 2 | May 7 – May 14 | Apr 30 – May 14 | Aug 8 – Aug 22 |
| Zucchini & Summer Squash | Mar 26 – Apr 2 | — | Apr 30 – May 14 | Aug 15 – Aug 29 |
| Winter Squash & Pumpkins | Mar 26 – Apr 2 | — | Apr 30 – May 14 | — |
| Melons & Watermelon | Mar 26 – Apr 2 | May 7 – May 21 | — | — |
| Carrots | — | — | Apr 2 – Apr 30 | Aug 1 – Aug 15 |
| Beets | — | — | Apr 2 – Apr 30 | Aug 15 – Aug 29 |
| Potatoes | — | — | Apr 2 – Apr 23 | — |
| Swiss Chard | — | — | Apr 9 – May 7 | Aug 15 – Aug 29 |
| Cilantro | — | — | Apr 9 – Apr 30 | Aug 29 – Sep 19 |
| Green Beans | — | — | Apr 30 – May 21 | Aug 8 – Aug 22 |
| Sweet Corn | — | — | Apr 30 – May 14 | — |
| Sweet Potatoes | — | May 7 – May 28 | — | — |
| Garlic | — | — | — | Oct 10 – Nov 14 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Grafton Wwtp, WI weather station, 2 km away (elevation 741 ft (226 m)).
Frost dates near Grafton
- Cedarburg Apr 23 · Oct 24
- Saukville May 5 · Oct 11
- Mequon Apr 23 · Oct 24
- Port Washington Apr 27 · Oct 22
- Newburg May 4 · Oct 11
- Jackson Apr 30 · Oct 15
- Fredonia May 5 · Oct 12
- Germantown May 6 · Oct 8
- Belgium May 5 · Oct 12
- Menomonee Falls May 6 · Oct 8
Frequently asked questions
When is the last frost in Grafton, WI?
The median last spring frost in Grafton, WI is April 23. There is still about a 10% chance of frost after May 9, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Grafton, WI?
The median first fall frost is October 24, with about a 10% chance of frost before October 8.
How long is the growing season in Grafton, WI?
About 184 days between the median last spring frost and first fall frost.
What planting zone is Grafton, WI?
Grafton, WI is in USDA hardiness zone 6a.