USDA hardiness zone lookup
Duluth, MN — USDA Zone 4a
Duluth, Minnesota · 124-day growing season
Frost dates and growing season in Duluth
| USDA hardiness zone | Zone 4a |
|---|---|
| Average last spring frost | May 22 |
| Average first fall frost | September 23 |
| Growing season length | ~124 days |
| Temperature range (F) | -30 to -20°F |
| Temperature range (C) | -34 to -29°C |
All of Duluth's mapped ZIP codes fall in the same hardiness band, Zone 4a.
These are 50%-probability averages modeled from Duluth's USDA hardiness zone and regional climate normals — not a single-station reading. In a typical year the last spring frost will have passed by May 22, but a colder-than-average year can run 1-2 weeks later. Plant tender crops (tomatoes, peppers, basil) once both soil and night temperatures are consistently warm — a thermometer beats the calendar.
Growing season in Duluth
Duluth, Minnesota sits in USDA Zone 4a, with roughly 124 frost-free days between an average last spring frost around May 22 and a first fall frost around September 23. That is a standard temperate season — most common vegetables finish comfortably, and a single main planting plus one succession round works well.
What grows in Duluth
Duluth falls in USDA Zone 4a, so the same hardiness constraints apply as the full Zone 4 guide. Vegetables, herbs, and fruit trees rated to Zone 4a (or hardier) will overwinter here in a typical year.
- Apple, pear, plum, sour cherry
- Blueberries (highbush)
- Raspberries
- Strawberries
- Tomatoes
- Peppers (short-season)
- Cucumbers
- Beans
- Squash (summer + winter)
- Garlic
What to plant in Duluth this week
Duluth's last frost is around May 22. This is the spring transplant window — start tomatoes and peppers indoors if you haven't, and direct-sow cold-tolerant crops now.
- When to plant tomatoes in zone 4
- When to plant peppers in zone 4
- When to plant basil in zone 4
- When to plant bush beans in zone 4
- When to plant cucumbers in zone 4
Full planting calendar for Duluth
Crop-by-crop sowing, transplant, and harvest dates calibrated to zone 4 averages:
- When to plant tomatoes in zone 4
- When to plant peppers in zone 4
- When to plant basil in zone 4
- When to plant garlic in zone 4
- When to plant lettuce in zone 4
- When to plant bush beans in zone 4
- When to plant cucumbers in zone 4
- When to plant summer squash in zone 4
- When to plant peas in zone 4
- When to plant carrots in zone 4
ZIP codes in Duluth
Drill down to the precise frost window and planting calendar for a specific ZIP in Duluth:
Local microclimate notes
Zone tables give you the average — but Duluthgardens vary. South-facing walls and paved areas can run a full half-zone warmer than the published rating. Low-lying spots, frost pockets, and shaded north sides can run colder. If you've gardened here a few seasons, your own frost record — the last time you actually got frost damage — beats any national average.
Source and methodology
Hardiness zone from the USDA Plant Hardiness Zone Map (2023 revision). Frost-date and growing-season figures are modeled from Duluth's USDA hardiness zone and regional NOAA 1991-2020 climate normals — zone-level estimates, not a per-station record, so treat them as planning guidance and confirm against your own local frost history. Crop recommendations draw on US Cooperative Extension references, curated by the Growli editorial team. Last reviewed June 2026.
Other cities in Minnesota
- Andover, MN — USDA Zone 4b
- Apple Valley, MN — USDA Zone 5a
- Burnsville, MN — USDA Zone 5a
- Mankato, MN — USDA Zone 5a
- Maple Grove, MN — USDA Zone 5a
- Minneapolis, MN — USDA Zone 5a
- Moorhead, MN — USDA Zone 4a
- Rochester, MN — USDA Zone 5a
- Saint Paul, MN — USDA Zone 5a
- St. Cloud, MN — USDA Zone 4b
- St. Louis Park, MN — USDA Zone 5a
- All of Minnesota by zone