USDA Plant Hardiness Zone
Zone 3a Frost Dates & Planting Calendar
19 ZIP codes across 2 states fall in zone 3a.
- Zone
- 3a
- Average Annual Low
- -40 to -35°F
- Typical Growing Season
- 110 days
- ZIP Codes
- 19
What zone 3a actually tells you
A hardiness zone describes one thing: the average coldest night of the year, which in zone 3a falls between -40 to -35°F. It answers whether a perennial will survive the winter — not when to plant in spring.
Frost dates answer the planting question, and they vary widely inside a single zone. Zone 3a spans 2 states, and a coastal ZIP can differ from an inland one by three weeks despite sharing the zone. Pick your own ZIP code below rather than planting by zone alone.