When to plant watermelons in Pennsylvania
Pennsylvania’s average last spring frost is May 1, and the first fall frost typically arrives around October 10 — about 162 frost-free days (USDA zones 5a, 5b, 6a, 6b, 7a, 7b). Watermelon needs 70–100 days to mature, which fits comfortably within Pennsylvania's growing season.
Pennsylvania covers a wide range of climates, so your exact frost dates may differ from the state average by two weeks or more. For dates tuned to your town, use the calendar generator.
When to plant watermelons in Pennsylvania: the short answer
For a spring planting, plant out May 8 – May 25, with seeds started indoors Apr 3 – Apr 17. Wait until the soil is at least 70°F and frost is over.
Windows are ~1–2 week bands around each date. Frost dates are a statewide average from NOAA/NCEI normals; your town may differ by two weeks or more. Calendar year 2026.
How to grow watermelons in Pennsylvania, step by step
- Start seeds indoors (Apr 3 – Apr 17). Sow seeds 1 inch deep in seed-starting mix under bright light. They take 4-10 days to sprout, fastest in soil around 85°F. Harden seedlings off for a week before they go outside.
- Prepare the bed. They need at least six to eight hours of direct sun a day and loose soil at least 24 inches deep, with a pH between 5.5 and 6.8. Dig in compost before planting.
- Plant out (May 8 – May 25). Space plants about 36 inches apart in rows 72 inches apart. It is killed by frost, so nothing goes outside until the danger has passed.
- Water and feed. Give it steady, even moisture, about an inch of water a week from rain or the hose.
- Watch for pests and problems. Pests: striped cucumber beetle, aphids, squash vine borer. Diseases and disorders: anthracnose, fusarium wilt, powdery mildew, gummy stem blight.
- Harvest (from about Jul 24 – Aug 23). Watermelon takes 70-100 days to reach harvest. Longest-season cucurbit here - icebox varieties (70-75 days) are the realistic choice north of the mid-Atlantic. Ripe when the curly tendril nearest the fruit is brown and dry and the ground spot is buttery yellow.
Figures come from our crop data; dates use Pennsylvania’s average frost dates. More in the full watermelon growing guide.
Watermelon planting dates by USDA zone in Pennsylvania
Pennsylvania spans USDA zones 5a, 5b, 6a, 6b, 7a, 7b. Colder zones, usually higher or further inland, have a later last spring frost and an earlier first fall frost than the state average, so the watermelon dates shift with them.
When to plant watermelons in nearby states
| State | Last frost | Plant out |
|---|---|---|
| Pennsylvania (this page) | May 1 | May 8 – May 25 |
| New Jersey | April 20 | Apr 27 – May 14 |
| Delaware | April 14 | Apr 21 – May 8 |
| Maryland | April 14 | Apr 21 – May 8 |
| District of Columbia | April 10 | Apr 17 – May 4 |
| Virginia | April 15 | Apr 22 – May 9 |
| West Virginia | May 5 | May 12 – May 29 |
Questions gardeners in Pennsylvania ask
When is the best time to plant watermelons in Pennsylvania?
Plant watermelon transplants outdoors in Pennsylvania between May 8 and May 25. That timing is set by Pennsylvania's average last spring frost of May 1; Pennsylvania spans several climates, so cooler and higher parts of the state run later.
When should I start watermelon seeds indoors in Pennsylvania?
Start seeds indoors between April 3 and April 17, about 3 weeks before the last frost, so the seedlings are ready to plant out from May 8.
What is the latest I can plant watermelons in Pennsylvania?
About August 1. Watermelons need at least 70 days to mature, and frost around October 10 ends the season, so later plantings risk being cut short.
When will watermelons planted in Pennsylvania be ready to harvest?
Planted on time, watermelons are usually ready from about July 24 to August 23, 70-100 days after planting.
When is the last frost in Pennsylvania?
On average around May 1, with the first fall frost around October 10 - about 162 frost-free days. Your town may differ by two weeks or more.