Portage, WI frost dates
Last spring frostApr 28median date
First fall frostOct 10median date
Growing season165 daysfrost-free
Hardiness zone5aZone 5a
How Portage compares
- In 8 years out of 10, the last spring frost in Portage falls between April 14 and May 12, a 28-day window. The first fall frost falls between September 26 and October 23.
- The median last frost is 7 days earlier than the Wisconsin median of May 5.
- Its 165-day growing season is longer than 75% of the 749 Wisconsin places with a regular frost season (state median 155 days).
- The last frost is 5 days earlier than the zone 5a median of May 3. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5a chart.
- The weather station records an average of 148 nights a year at or below 32°F.
- Compared with Madison, WI, 53 km away, the last frost here is 3 days earlier than there and the growing season is 4 days longer.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 14 |
| 50% (median) | April 28 |
| 10% (safe for tender plants) | May 12 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 26 |
| 50% (median) | October 10 |
| 90% (late) | October 23 |
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 Portage, WI
Portage, WI frost dates — last frost Apr 28, first frost Oct 10, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Feb 3 to Feb 17Transplant outside: Mar 31 to Apr 14
Start indoors: Feb 17 to Mar 3Transplant outside: May 12 to May 26
Start indoors: Feb 17 to Mar 3Transplant outside: May 12 to May 26
Start indoors: Mar 3 to Mar 17Transplant outside: May 5 to May 19
Start indoors: Mar 3 to Mar 17Transplant outside: Apr 7 to Apr 21Sow outdoors: Mar 31 to May 5Plant for fall: Aug 15 to Sep 12
Start indoors: Mar 3 to Mar 17Transplant outside: Mar 31 to Apr 14Sow outdoors: Mar 31 to Apr 14Plant for fall: Aug 1 to Aug 22
Start indoors: Mar 3 to Mar 17Transplant outside: Apr 14 to Apr 28Plant for fall: Jul 4 to Jul 25
Start indoors: Mar 3 to Mar 17Transplant outside: Apr 7 to Apr 21Plant for fall: Jul 4 to Jul 25
Start indoors: Mar 3 to Mar 17Transplant outside: Apr 14 to Apr 28Plant for fall: Jul 4 to Jul 25
Start indoors: Mar 17 to Mar 31Transplant outside: May 19 to Jun 2Sow outdoors: May 19 to Jun 2
Start indoors: Mar 17 to Mar 31Transplant outside: May 5 to May 19
Sow outdoors: Mar 17 to Apr 7Plant for fall: Jul 18 to Aug 8
Sow outdoors: Mar 17 to Apr 7Plant for fall: Aug 15 to Sep 5
Sow outdoors: Mar 24 to May 5Plant for fall: Aug 29 to Sep 19
Start indoors: Mar 31 to Apr 7Transplant outside: May 12 to May 19Sow outdoors: May 5 to May 19Plant for fall: Jul 25 to Aug 8
Start indoors: Mar 31 to Apr 7Sow outdoors: May 5 to May 19Plant for fall: Aug 1 to Aug 15
Start indoors: Mar 31 to Apr 7Sow outdoors: May 5 to May 19
Start indoors: Mar 31 to Apr 7Transplant outside: May 12 to May 26
Sow outdoors: Apr 7 to May 5Plant for fall: Jul 18 to Aug 1
Sow outdoors: Apr 7 to May 5Plant for fall: Aug 1 to Aug 15
Sow outdoors: Apr 7 to Apr 28
Sow outdoors: Apr 14 to May 12Plant for fall: Aug 1 to Aug 15
Sow outdoors: Apr 14 to May 5Plant for fall: Aug 15 to Sep 5
Sow outdoors: May 5 to May 26Plant for fall: Jul 25 to Aug 8
Sow outdoors: May 5 to May 19
Transplant outside: May 12 to Jun 2
Plant for fall: Sep 26 to Oct 31
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Portage, WI
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 3 – Feb 17 | Mar 31 – Apr 14 | — | — |
| Peppers | Feb 17 – Mar 3 | May 12 – May 26 | — | — |
| Eggplant | Feb 17 – Mar 3 | May 12 – May 26 | — | — |
| Tomatoes | Mar 3 – Mar 17 | May 5 – May 19 | — | — |
| Lettuce | Mar 3 – Mar 17 | Apr 7 – Apr 21 | Mar 31 – May 5 | Aug 15 – Sep 12 |
| Kale | Mar 3 – Mar 17 | Mar 31 – Apr 14 | Mar 31 – Apr 14 | Aug 1 – Aug 22 |
| Broccoli | Mar 3 – Mar 17 | Apr 14 – Apr 28 | — | Jul 4 – Jul 25 |
| Cabbage | Mar 3 – Mar 17 | Apr 7 – Apr 21 | — | Jul 4 – Jul 25 |
| Cauliflower | Mar 3 – Mar 17 | Apr 14 – Apr 28 | — | Jul 4 – Jul 25 |
| Okra | Mar 17 – Mar 31 | May 19 – Jun 2 | May 19 – Jun 2 | — |
| Basil | Mar 17 – Mar 31 | May 5 – May 19 | — | — |
| Peas | — | — | Mar 17 – Apr 7 | Jul 18 – Aug 8 |
| Spinach | — | — | Mar 17 – Apr 7 | Aug 15 – Sep 5 |
| Radishes | — | — | Mar 24 – May 5 | Aug 29 – Sep 19 |
| Cucumbers | Mar 31 – Apr 7 | May 12 – May 19 | May 5 – May 19 | Jul 25 – Aug 8 |
| Zucchini & Summer Squash | Mar 31 – Apr 7 | — | May 5 – May 19 | Aug 1 – Aug 15 |
| Winter Squash & Pumpkins | Mar 31 – Apr 7 | — | May 5 – May 19 | — |
| Melons & Watermelon | Mar 31 – Apr 7 | May 12 – May 26 | — | — |
| Carrots | — | — | Apr 7 – May 5 | Jul 18 – Aug 1 |
| Beets | — | — | Apr 7 – May 5 | Aug 1 – Aug 15 |
| Potatoes | — | — | Apr 7 – Apr 28 | — |
| Swiss Chard | — | — | Apr 14 – May 12 | Aug 1 – Aug 15 |
| Cilantro | — | — | Apr 14 – May 5 | Aug 15 – Sep 5 |
| Green Beans | — | — | May 5 – May 26 | Jul 25 – Aug 8 |
| Sweet Corn | — | — | May 5 – May 19 | — |
| Sweet Potatoes | — | May 12 – Jun 2 | — | — |
| Garlic | — | — | — | Sep 26 – Oct 31 |
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 Portage Wwtp, WI weather station, 3 km away (elevation 784 ft (239 m)).
Frost dates near Portage
- Pardeeville Apr 28 · Oct 10
- Wyocena Apr 28 · Oct 10
- Endeavor May 3 · Oct 5
- Briggsville May 8 · Oct 3
- Poynette May 4 · Oct 6
- Merrimac May 1 · Oct 10
- Baraboo May 5 · Oct 5
- Rio May 4 · Oct 6
- Packwaukee May 3 · Oct 5
- Lodi May 1 · Oct 10
Frequently asked questions
When is the last frost in Portage, WI?
The median last spring frost in Portage, WI is April 28. There is still about a 10% chance of frost after May 12, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Portage, WI?
The median first fall frost is October 10, with about a 10% chance of frost before September 26.
How long is the growing season in Portage, WI?
About 165 days between the median last spring frost and first fall frost.
What planting zone is Portage, WI?
Portage, WI is in USDA hardiness zone 5a.