USDA hardiness zone
Zone 4b
Rolled up from the 1,337 ZIP codes in our data that are classified zone 4b, covering 583 nurseries and garden centers across 210 cities we track in this zone.
Average minimum winter temperature
-25°F
Last spring frost range
Apr 22–Jun 20
First fall frost range
Aug 21–Oct 21
Average frost-free growing season
143 days
Average monthly temperature
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 15.2° | 18.7° | 29.9° | 42.7° | 54.9° | 64.5° | 69.5° | 67.6° | 59.3° | 46.1° | 32.5° | 20.7° |
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 22–Jun 20. 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 4b means an average annual extreme minimum winter temperature of -25°F to -20°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 here carries its zone matched by centroid against the map, not by its polygon boundary, via phzmapi.org's ZIP-level derivation.
The last-frost range above covers roughly two months across this zone's own ZIPs. A gardener in one 4b town can be transplanting a tender crop while another, in the same zone, is still weeks from a safe last frost; that gap is the reason every crop guide on this site recomputes against your own ZIP rather than this page's median.
We track nurseries across Minnesota, Montana, North Dakota, New York, Wisconsin, and Wyoming in zone 4b, with Rochester, MN and Eau Claire, WI carrying the most of any city here.
Cities we track in zone 4b
- Rochester, MN (19)
- Eau Claire, WI (19)
- Wausau, WI (15)
- River Falls, WI (14)
- Hudson, WI (12)
- New Richmond, WI (11)
- Duluth, MN (10)
- Marshfield, WI (10)
- Merrill, WI (9)
- Rhinelander, WI (9)
- Chippewa Fls, WI (9)
- Great Falls, MT (9)
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).