Why these dates work in zone 4b
Zone 4b's last spring frost averages May 15 and first fall frost Sep 25 — about 133 frost-free days. Watermelon 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. Starting seeds indoors 4 weeks ahead gives strong transplants ready the moment the soil warms.
Common questions
How long does watermelon take to grow in zone 4b?
Watermelon matures in about 70–90 days from transplanting. In zone 4b that means setting plants out around May 29 and first picking around Aug 7.
Will watermelon survive frost in zone 4b?
No — watermelon is frost-sensitive. In zone 4b, wait until after the last frost (around May 15) to plant, and harvest before the first fall frost (around Sep 25).
For soil, spacing, pests and companion planting, see the full watermelon growing guide →