When to plant in Portage, WI
USDA Zone 5aEverything below — frost dates, hardiness zone, and what to plant when in Portage, Wisconsin — is derived from the closest NOAA station with complete climate normals.
Zone 5a means Portage sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
The average first fall frost in Portage is now 7 days later than in the 1981–2010 normals. See how frost dates are shifting nationwide →
Frost probability
PORTAGE WWTP · 1991–2020The date the last spring and first fall frost occur, by threshold and probability. A 90% date is later in spring — and earlier in fall — than a 10% date; the 50% · 32°F row is what most gardeners plan around. These are Portage’s own odds, recorded at PORTAGE WWTP.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 24 | May 8 | Apr 26 | Sep 17 | Sep 30 | Oct 11 |
| 32°F | May 12 | Apr 28 | Apr 14 | Sep 26 | Oct 10 | Oct 23 |
| 28°F | Apr 30 | Apr 16 | Apr 4 | Oct 6 | Oct 22 | Nov 4 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Full-year planting calendar
Each bar is the exact window to take a planting action in Portage, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 24 km · complete 32°F normalsWhen stations disagree by more than a few days, that spread is real microclimate variation — elevation, water, urban heat. Judge which station best matches your own yard.
Portage planting FAQ
When is the last spring frost in Portage, WI?
Portage's average last spring frost falls near April 28 — the 50% mark at 32°F in the 1991–2020 normals. Hold tender transplants until the risk has passed, then plant out.
When is the first fall frost in Portage, WI?
The first fall frost in Portage typically arrives around October 10 (50% probability at 32°F). Harvest or protect frost-sensitive crops before then.
What hardiness zone is Portage in?
Portage is in USDA hardiness zone 5a. In zone 5a, winters are cold — pick cold-hardy varieties and protect tender crops.
How long is the growing season in Portage?
There are roughly 165 frost-free days in Portage (a moderate growing season), running from the average last frost around April 28 to the first fall frost near October 10.
When should I plant tomatoes in Portage?
In Portage, start tomato seeds indoors around March 3–March 17, then transplant seedlings outdoors around May 5 once the danger of frost has passed.
Never miss a window in Portage
An email when it’s time to start seeds, transplant, and sow — timed to Portage’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Baraboo · 24 km
- DeForest · 37 km
- Waunakee · 41 km
- Reedsburg · 43 km
- Sun Prairie · 45 km
- Middleton · 49 km
- Madison · 51 km
- Beaver Dam · 52 km
Frost dates recorded at PORTAGE WWTP, 3 km from the city center · 1991–2020 NOAA climate normals · zone from the USDA/PRISM 2023 map. How we compute this.
BlissGarden. "When to Plant in Portage, WI — Frost Dates & Zone 5a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00476718. Retrieved from https://blissgarden.com/wisconsin/portage.