Zone 4a Frost Dates & Planting Calendar

What zone 4a actually tells you

A hardiness zone describes one thing: the average coldest night of the year, which in zone 4a falls between -30 to -25°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 4a spans 17 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.