When to plant Watermelon in Flathead County, MT
Plant Watermelon in Flathead County, between June 10 and July 1 — the only viable window. Zone 5a's short season (99 frost-free days) rules out a fall crop.
When to Plant Watermelon in Flathead County, MT
Watermelon is a sprawling vine crop that produces sweet, juicy fruits in hot weather. Varieties range from personal-sized icebox types to 50-pound giants.
Flathead County, Montana is in USDA Zone 5a. The average last spring frost is June 3 and the first fall frost is September 10, giving you a growing season of approximately 99 days.
At an elevation of 6,233 feet, Flathead County receives approximately 20.7 inches of rainfall annually with predominantly loam soil. Summer highs average 87°F, providing good warmth for Watermelon during the growing season.
Flathead County Soil Profile
Soil Type
Loam
Soil pH
6.0-7.0
Drainage
Well Drained
How Much Watermelon to Grow
For a family of 4, plant approximately 4 watermelon plants in about 8 sq ft. In Flathead County's 99-day season, you'll have plenty of time for a full harvest. Plan your garden layout →
Watermelon Planting Timeline — Flathead County, MT
Watermelon Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 29 | Apr 29 – May 13 |
| Transplant Outdoors | June 17 | Jun 17 – Jul 1 |
| Direct Sow | June 10 | Jun 10 – Jul 1 |
| Harvest | August 26 | Aug 26 – Oct 14 |
Plant 1" deep · 30" apart · Rows 42" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors |
| May | Start Indoors |
| June | Transplant Outdoors Direct Sow |
| July | Transplant Outdoors Direct Sow |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
Moderate — regular watering
📅 Days to Maturity
70–100 days
🧪 Soil pH
Needs 6–7.5 · Your soil: N/A
🗺️ USDA Zone
Zone 5a
📆 Growing Season
99 days in Flathead County
Growing Tips for Flathead County
Start seeds indoors 3-4 weeks early or direct sow after soil is warm. Plant on mounds with plenty of space. Check ripeness by looking for a yellow ground spot and dull thump when tapped.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Watermelon in Other Locations
Frequently Asked Questions
When should I plant Watermelon in Flathead County, MT?
Flathead County is in Zone 5a with an average last frost of June 3. Plan your Watermelon planting based on this frost date — see the calendar above for exact timing.
What planting zone is Flathead County, MT?
Flathead County, Montana is in USDA Hardiness Zone 5a. The average last spring frost is June 3 and first fall frost is September 10.
When should I plant Watermelon in Flathead County, MT?
In Flathead County, MT, plant Watermelon after the last frost (around June 3) and before the first frost (around September 10). Best results when soil holds above 50°F.
What growing zone is Flathead County, MT for Watermelon?
Flathead County sits in USDA Zone 5a. Watermelon grows reliably in zones 4a through 11b, so it's a good fit here.
Can Watermelon grow in Flathead County's climate?
Yes — Watermelon grows well in Flathead County's temperate climate. Flathead County averages a 99-day frost-free season, with last frost around June 3 and first frost around September 10.
Your Flathead County Garden Planner — Free
A 22-page printable planner built for Flathead County (Zone 5a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.