When to plant watermelons in Wyoming
Wyoming’s average last spring frost is May 20, and the first fall frost typically arrives around September 15 — about 118 frost-free days (USDA zones 3a, 3b, 4a, 4b, 5a, 6a). Watermelon needs 70–100 days to mature, which fits comfortably within Wyoming's growing season.
Wyoming 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 Wyoming: the short answer
For a spring planting, plant out May 27 – Jun 13, with seeds started indoors Apr 22 – May 6. 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 Wyoming, step by step
- Start seeds indoors (Apr 22 – May 6). 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 27 – Jun 13). 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 Aug 12 – Sep 11). 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 Wyoming’s average frost dates. More in the full watermelon growing guide.
Watermelon planting dates by USDA zone in Wyoming
Wyoming spans USDA zones 3a, 3b, 4a, 4b, 5a, 6a. 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
Questions gardeners in Wyoming ask
When is the best time to plant watermelons in Wyoming?
Plant watermelon transplants outdoors in Wyoming between May 27 and June 13. That timing is set by Wyoming's average last spring frost of May 20; Wyoming spans several climates, so cooler and higher parts of the state run later.
When should I start watermelon seeds indoors in Wyoming?
Start seeds indoors between April 22 and May 6, about 3 weeks before the last frost, so the seedlings are ready to plant out from May 27.
What is the latest I can plant watermelons in Wyoming?
About July 7. Watermelons need at least 70 days to mature, and frost around September 15 ends the season, so later plantings risk being cut short.
When will watermelons planted in Wyoming be ready to harvest?
Planted on time, watermelons are usually ready from about August 12 to September 11, 70-100 days after planting.
When is the last frost in Wyoming?
On average around May 20, with the first fall frost around September 15 - about 118 frost-free days. Your town may differ by two weeks or more.