Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Zone 4b

In USDA zone 4b the coldest night of an average winter reaches −25 to −20 °F (−31.7 to −28.9 °C). 1,284 ZIP codes (3.2% of all) are in this zone.

Zone4b−25 to −20 °F
Coldest night−31.7 to −28.9 °C
ZIP codes1,284
Typical last frostMay 8
Typical first frostOct 1

Frost dates vary within zone 4b

For the middle half of zone-4b ZIP codes the last spring frost falls between May 5 and May 17, and the first fall frost between Sep 27 and Oct 4. The zone measures winter cold, not season length: humid Eastern and dry Western towns in the same zone can be weeks apart. Use your ZIP code for a planting date.

States with zone 4b

Minnesota344 ZIPsWisconsin238 ZIPsSouth Dakota183 ZIPsMontana129 ZIPsNew York107 ZIPsVermont70 ZIPsWyoming43 ZIPsMichigan38 ZIPsNorth Dakota35 ZIPsMaine30 ZIPsAlaska28 ZIPsIowa17 ZIPsColorado10 ZIPsNew Hampshire10 ZIPsIdaho2 ZIPs

Cities mostly in zone 4b

Duluth, MN13 ZIPsSaint Cloud, MN11 ZIPsHelena, MT7 ZIPsMontpelier, VT7 ZIPsRochester, MN5 ZIPsGreat Falls, MT5 ZIPsMaple Plain, MN4 ZIPsWausau, WI3 ZIPsEau Claire, WI3 ZIPsJamestown, ND3 ZIPsSteamboat Springs, CO3 ZIPsNewcomb, NY2 ZIPs

← Zone 4a (colder)Zone 5a (warmer) →

Questions

What is the temperature range of zone 4b?

Zone 4b covers places where the coldest night of an average winter (the annual extreme minimum averaged over 1991–2020) is −25 to −20 °F, or −31.7 to −28.9 °C.

When is the last frost in zone 4b?

Across ZIP codes in zone 4b, the median last spring frost falls between May 5 and May 17 for the middle half of places. Zone alone doesn't set the frost date — check your ZIP code.

Which states have zone 4b?

Zone 4b occurs in 15 states; the most ZIP codes are in Minnesota, Wisconsin, South Dakota, Montana, New York.

What can I grow in zone 4b?

Perennials, shrubs and trees labeled hardy to zone 4b or a lower (colder) number should survive a typical winter. Annual vegetables depend on frost dates rather than zone.

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.