Frost dates · USDA zone 4b
Frost dates for Duluth, MN
Duluth, MN sees its last 32 °F night of spring around May 14 and its first of fall around October 12 — a 149-day freeze-free season in a typical year.
Pick a sauce; the Plan Builder runs this station's dates and hands back the calendar, plant count and gear list.
Freeze odds, by date
| Odds | Last spring freeze after | First fall freeze before |
|---|---|---|
| 9 years in 10 | Apr 24 | Oct 26 |
| Median — 1 year in 2 | May 14 | Oct 12 |
| 1 year in 10 | Jun 1 | Sep 25 |
The top row is the risky edge: in 9 years of 10 a spring freeze still comes after it, so tender transplants set out then need cover. The bottom row is the cautious date — only 1 year in 10 freezes after it — and the one to plan uncovered tender transplants against. Freeze-free season: 149 days median, at least 124 in 9 years of 10, at least 175 days in 1 year of 10. NOAA ranks season length year by year, so it is not the gap between two rows above. A hard freeze (28 °F) has a median last date of Apr 29 and first of Oct 25.
Duluth planting calendar, 2027
Every row runs from the median last frost (May 14) and median first frost (Oct 12) above, using each cultivar's days to maturity. Same engine as the Plan Builder.
| Crop | Start indoors | Transplant / plant | First harvest | Days |
|---|---|---|---|---|
| Hardneck GarlicSiberian (porcelain hardneck) | — | Oct 15prior fall | Jun 12 | 240 from sow |
| Spanish OnionYellow Sweet Spanish (long-day) | Feb 19 | Apr 16 | Aug 4 | 110 from transplant |
| Mustard greensGarnet Giant (Brassica juncea) | Direct sow | May 14 | Jun 13 | 30 from sow |
| CilantroSlow Bolt (Coriandrum sativum) | Apr 30 | Apr 30 | Jun 14 | 45 from sow |
| Genovese BasilGenovese | Apr 16 | May 28 | Jul 27 | 60 from transplant |
| CayenneLong Slim Cayenne (Capsicum annuum) | Mar 19 | May 21 | Aug 4 | 75 from transplant |
| HabaneroOrange Habanero (Capsicum chinense) | Mar 5 | May 28 | Aug 31 | 95 from transplant |
| JalapeñoEarly Jalapeño (Capsicum annuum) | Mar 19 | May 21 | Aug 4 | 75 from transplant |
| Marconi Red PepperMarconi Red (Capsicum annuum) | Mar 19 | May 21 | Aug 9 | 80 from transplant |
| SerranoSerrano Tampiqueño (Capsicum annuum) | Mar 19 | May 21 | Aug 9 | 80 from transplant |
| Nantes CarrotScarlet Nantes | Apr 30 | Apr 30 | Jul 9 | 70 from sow |
| TomatilloToma Verde | Apr 2 | May 21 | Jul 30 | 70 from transplant |
| Roma TomatoRoma VF (determinate paste) | Apr 2 | May 21 | Aug 4 | 75 from transplant |
| San Marzano TomatoSan Marzano (indeterminate paste) | Apr 2 | May 21 | Aug 9 | 80 from transplant |
Tight means first harvest lands within two weeks of the median first fall frost: start that crop indoors on time or cover it in fall.
What sauce can Duluth grow?
Each sauce, scheduled for a Duluth container garden: when the first seeds go in and when enough fruit has ripened for one batch.
Duluth frost questions
When is the last frost in Duluth, MN?
The median last 32 °F freeze at DULUTH HARBOR STN, MN is May 14: half of years see a later one. One year in ten, a freeze still comes after June 1; nine years in ten, it comes after April 24. Source: NOAA NCEI 1991–2020 U.S. Climate Normals.
When is the first frost in Duluth, MN?
The median first 32 °F freeze of fall is October 12. One year in ten it arrives before September 25; nine years in ten, before October 26.
How long is the growing season in Duluth, MN?
149 days between the last spring and first fall 32 °F freeze in a median year. Nine years in ten the season runs at least 124 days; one year in ten, at least 175 days.
What growing zone is Duluth, MN?
USDA hardiness zone 4b, per the 2023 USDA Plant Hardiness Zone Map for ZIP 55806. A zone describes the coldest winter night, not when frost ends, so it is the wrong number for a planting calendar — the frost dates on this page are the right one.
When should I plant tomatoes in Duluth, MN?
Start Roma VF (determinate paste) seeds indoors around Apr 2 and transplant around May 21, 1 week after the median last frost. To cut the freeze risk to one year in ten, wait for Jun 1. First ripe fruit lands around Aug 4.
When should I plant peppers in Duluth, MN?
Sow jalapeño indoors on a heat mat around Mar 19; transplant no earlier than May 21, and wait past it until nights hold above 50 °F — that can run weeks later. First green pods around Aug 4.
Nearby in Minnesota
- Blainelast frost May 5
- Coon Rapidslast frost May 5
- Brooklyn Parklast frost Apr 30
- St. Cloudlast frost May 3
- Maple Grovelast frost Apr 30
- St. Paullast frost Apr 24
All Minnesota frost dates → · How frost-date math drives a sowing calendar →