When to plant in Duluth, MN
USDA Zone 4bEverything below — frost dates, hardiness zone, and what to plant when in Duluth, Minnesota — is derived from the closest NOAA station with complete climate normals.
Zone 4b is cold — in Duluth, most perennials must be fully hardy, and your frost dates set a tight window for tender annual vegetables.
Frost probability
DULUTH HARBOR STN · 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 Duluth’s own odds, recorded at DULUTH HARBOR STN.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | Jun 16 | May 31 | May 12 | Sep 12 | Sep 30 | Oct 14 |
| 32°F | Jun 1 | May 14 | Apr 24 | Sep 25 | Oct 12 | Oct 26 |
| 28°F | May 18 | Apr 29 | Apr 11 | Oct 9 | Oct 25 | Nov 7 |
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 Duluth, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 9 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.
Duluth planting FAQ
When is the last spring frost in Duluth, MN?
Duluth's average last spring frost falls near May 14 — 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 Duluth, MN?
In Duluth, the first 32°F freeze of fall lands around October 12 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Duluth in?
Duluth is in USDA hardiness zone 4b. In zone 4b, winters are cold — pick cold-hardy varieties and protect tender crops.
How long is the growing season in Duluth?
There are roughly 151 frost-free days in Duluth (a moderate growing season), running from the average last frost around May 14 to the first fall frost near October 12.
When should I plant tomatoes in Duluth?
In Duluth, start tomato seeds indoors around March 19–April 2, then transplant seedlings outdoors around May 21 once the danger of frost has passed.
Never miss a window in Duluth
An email when it’s time to start seeds, transplant, and sow — timed to Duluth’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Hermantown · 9 km
- Superior · 10 km
- Cloquet · 29 km
- Hibbing · 93 km
- Grand Rapids · 118 km
- North Branch · 154 km
- Cambridge · 159 km
- Brainerd · 165 km
Frost dates recorded at DULUTH HARBOR STN, 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 Duluth, MN — Frost Dates & Zone 4b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00212246. Retrieved from https://blissgarden.com/minnesota/duluth.