USDA hardiness zone
Zone 4a
Rolled up from the 829 ZIP codes in our data that are classified zone 4a, covering 155 nurseries and garden centers across 59 cities we track in this zone.
Average minimum winter temperature
-30°F
Last spring frost range
Apr 30–Jun 24
First fall frost range
Aug 25–Oct 13
Average frost-free growing season
136 days
Average monthly temperature
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 10.7° | 14.7° | 26.8° | 40.9° | 53.8° | 63.5° | 68.5° | 66.8° | 57.9° | 44° | 29.3° | 16.7° |
NOAA 1991–2020 Climate Normals, averaged across this zone's member ZIPs.
Crops by frost hardiness
What grows here, and when
This zone's own last-frost dates range across Apr 30–Jun 24. Hardy and semi-hardy crops can go in before that date; tender and very-tender crops need to wait until after it. See each crop's own guide for exact windows at a specific location in this zone.
Planting windows and crop timing here are computed from USDA/NOAA climate data and the university extension sources cited below, not a site visit or soil test. Treat this as a starting point: local conditions vary, and a local nursery or extension office can advise on your exact site. See our full Disclaimer.
Hardy (49)
- Apple (bare-root fruit tree)
- Apricot (bare-root fruit tree)
- Asparagus
- Bachelor's Button (Cornflower)
- Bare-root rose
- Blackberry
- Blueberry
- Broccoli
- Brussels Sprouts
- Cabbage
- Calendula
- Catnip/Catmint
- Cherry (sweet/tart, bare-root fruit tree)
- Chives
- Collards
- Currant
- Deciduous shade tree (generic, e.g. maple/oak, bare-root or B&B)
- Elderberry
- Evergreen shrub (B&B/potted, e.g. arborvitae, boxwood)
- Flowering deciduous shrub (generic, e.g. lilac/forsythia)
- Garden Peas
- Garlic
- Gooseberry
- Kale
- Kohlrabi
- Larkspur
- Lavender
- Lettuce
- Mint
- Onion (bulb)
- Oregano
- Peach (bare-root fruit tree)
- Pear (bare-root fruit tree)
- Plum (bare-root fruit tree)
- Radish
- Raspberry
- Rhubarb
- Rutabaga
- Sage
- Snapdragon
- Snow Peas
- Spinach
- Strawberry
- Sweet Alyssum
- Sweet Pea
- Table/Bunch Grape
- Tarragon
- Thyme
- Turnip
Semi-hardy (16)
Tender (20)
Zone 4a means an average annual extreme minimum winter temperature of -30°F to -25°F on the 2023 USDA Plant Hardiness Zone Map (USDA/ARS with the PRISM Climate Group at Oregon State University, 1991-2020 records). Every ZIP in this rollup carries its zone matched by centroid against the map, not by its polygon boundary, through phzmapi.org's ZIP-level derivation.
The last-frost range above spans close to two months across this zone's own ZIPs, wide enough that this zone's own median date is a starting point, not your date. That width is elevation and geography, not measurement error: 4a runs from the Great Lakes basin out onto the plains, and those two settings don't share a spring.
We track nurseries across Michigan, Minnesota, North Dakota, New York, and Wisconsin in zone 4a, with the heaviest counts around Bismarck and Fargo, ND, both on the plains side of this band rather than the upper-Midwest side where most of this zone's own ZIPs sit.
Cities we track in zone 4a
- Bismarck, ND (16)
- Fargo, ND (14)
- Hayward, WI (11)
- Grand Forks, ND (7)
- Minot, ND (6)
- Spooner, WI (5)
- West Fargo, ND (5)
- Saint Croix Fls, WI (5)
- Tomahawk, WI (4)
- Tupper Lake, NY (4)
- Saranac Lake, NY (4)
- Minocqua, WI (4)
Nearby zones
All zones
USDA 2023 Plant Hardiness Zone Map (zone boundaries, via the phzmapi.org ZIP-level derivation) and NOAA 1991–2020 Climate Normals (frost dates, growing season, monthly temperatures).