When to Plant Watermelon in Colorado: Best Months and Last Planting Date
Plant watermelon in Colorado from late May to mid June, after frost and 65°F soil. See Front Range, western valley, and mountain timing plus variety picks.
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When to Plant Watermelon in Colorado
Plant watermelon in Colorado after the last frost and once soil has warmed to at least 65 degrees F, which for most gardens means late May to mid June. Colorado's altitude, cool nights, and short frost-free season make it one of the more challenging watermelon states, but the famous Rocky Ford melon country proves it can be done well.
The Front Range and lower elevations along the eastern plains usually plant in late May to early June. The Arkansas Valley around Rocky Ford, one of the warmest melon regions in the state, can often plant in mid to late May. Western valleys like Grand Junction fit late May. Mountain towns above 7,000 feet rarely have enough season for watermelon outdoors — use a greenhouse, a low tunnel (a mini hoop cover over the bed), or grow faster crops instead. Use the watermelon by zone guide with your local frost date.
Colorado Timing Notes
- Start seeds indoors 3 to 4 weeks before transplanting — transplants are strongly recommended at altitude.
- Use black plastic mulch and row cover (a light garden fabric that holds in warmth); Colorado nights stay cool even in summer, and trapped daytime heat speeds vines significantly.
- Choose a 70 to 75 day short-season or icebox variety (a small, refrigerator-sized melon).
- Pick a south-facing bed sheltered from hail-prone exposure if you can.
Is It Too Late to Plant Watermelon in Colorado?
Colorado's window closes fast. A short-season variety transplanted by mid June can ripen before the typical late September to early October frost at lower elevations. Past mid June, seed will not make it; a large transplant plus row cover in September is the only realistic late option.
Next Steps
Check your local frost dates — they vary enormously with elevation. Warm the soil with black plastic, transplant a short-season variety, and keep row cover handy for both June cold snaps and September frost.