Zone 5a covers 27 days of last-frost dates. We measured Sioux City, IA at Apr 20 and Bozeman, MT at May 17. Give us your town or ZIP and we'll use ten years of daily lows recorded at your own coordinates instead of the middle of that range.
Why these dates work in zone 5a
Zone 5a's last spring frost averages Apr 30 and first fall frost Oct 20 — about 173 frost-free days. Corn is frost-sensitive, so the 2w after frost timing builds in a safety margin against a late cold snap — setting plants out too early risks losing them to frost.
Common questions
How long does corn take to grow in zone 5a?
Corn matures in about 70–90 days from sowing. In zone 5a that means sowing around May 14 and first picking around Jul 23.
Will corn survive frost in zone 5a?
No — corn is frost-sensitive. In zone 5a, wait until after the last frost (around Apr 30) to plant, and harvest before the first fall frost (around Oct 20).
For soil, spacing, pests and companion planting, see the full corn growing guide →