Zone 3b
In USDA zone 3b the coldest night of an average winter reaches −35 to −30 °F (−37.2 to −34.4 °C). 230 ZIP codes (0.6% of all) are in this zone.
Frost dates vary within zone 3b
For the middle half of zone-3b ZIP codes the last spring frost falls between May 15 and May 24, and the first fall frost between Sep 18 and Sep 27. 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 3b
Cities mostly in zone 3b
← Zone 3a (colder)Zone 4a (warmer) →
Questions
What is the temperature range of zone 3b?
Zone 3b covers places where the coldest night of an average winter (the annual extreme minimum averaged over 1991–2020) is −35 to −30 °F, or −37.2 to −34.4 °C.
When is the last frost in zone 3b?
Across ZIP codes in zone 3b, the median last spring frost falls between May 15 and May 24 for the middle half of places. Zone alone doesn't set the frost date — check your ZIP code.
Which states have zone 3b?
Zone 3b occurs in 6 states; the most ZIP codes are in Minnesota, North Dakota, Alaska, Montana, Wisconsin.
What can I grow in zone 3b?
Perennials, shrubs and trees labeled hardy to zone 3b 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.