Zone 3a
In USDA zone 3a the coldest night of an average winter reaches −40 to −35 °F (−40 to −37.2 °C). 23 ZIP codes (0.1% of all) are in this zone.
Frost dates vary within zone 3a
For the middle half of zone-3a ZIP codes the last spring frost falls between May 28 and Jun 5, and the first fall frost between Sep 3 and Sep 14. 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 3a
← Zone 2b (colder)Zone 3b (warmer) →
Questions
What is the temperature range of zone 3a?
Zone 3a covers places where the coldest night of an average winter (the annual extreme minimum averaged over 1991–2020) is −40 to −35 °F, or −40 to −37.2 °C.
When is the last frost in zone 3a?
Across ZIP codes in zone 3a, the median last spring frost falls between May 28 and Jun 5 for the middle half of places. Zone alone doesn't set the frost date — check your ZIP code.
Which states have zone 3a?
Zone 3a occurs in 2 states; the most ZIP codes are in Alaska, Minnesota.
What can I grow in zone 3a?
Perennials, shrubs and trees labeled hardy to zone 3a 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.