USDA Plant Hardiness Zone
Zone 1a Frost Dates & Planting Calendar
2 ZIP codes across 1 states fall in zone 1a.
- Zone
- 1a
- Average Annual Low
- -60 to -55°F
- Typical Growing Season
- 93 days
- ZIP Codes
- 2
What zone 1a actually tells you
A hardiness zone describes one thing: the average coldest night of the year, which in zone 1a falls between -60 to -55°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 1a spans 1 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.