When to Plant Watermelon in Bonner County, ID
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.
Bonner County, Idaho is in USDA Zone 5b. The average last spring frost is May 5 and the first fall frost is October 3, giving you a growing season of approximately 151 days.
At an elevation of 7,480 feet, Bonner County receives approximately 12.9 inches of rainfall annually with predominantly loam soil. Summer highs average 86°F, providing good warmth for Watermelon during the growing season. With low rainfall, drip irrigation is essential for growing Watermelon successfully. Mulch heavily to conserve soil moisture.
Bonner County Soil Profile
Soil Type
Loam
Soil pH
6.4-8.2
Drainage
Well Drained
Plant Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Watermelon Planting Timeline — Bonner County, ID
Watermelon Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 31 | Mar 31 – Apr 14 |
| Transplant Outdoors | May 19 | May 19 – Jun 2 |
| Direct Sow | May 12 | May 12 – Jun 2 |
| Harvest | July 28 | Jul 28 – Sep 15 |
Plant 1" deep · 30" apart · Rows 42" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors |
| May | Transplant Outdoors Direct Sow |
| June | Transplant Outdoors Direct Sow |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
Sun
Full Sun (6-8+ hours)
Water
Moderate — regular watering
Days to Maturity
70–100 days
Soil pH
6 – 7.5
USDA Zone
Zone 5b
Growing Season
151 days
Growing Tips for Bonner 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
Level Up Your Garden
Watermelon in Other Locations
Frequently Asked Questions
When should I plant Watermelon in Bonner County, ID?
Bonner County is in Zone 5b with an average last frost of May 5. Plan your Watermelon planting based on this frost date — see the calendar above for exact timing.
What planting zone is Bonner County, ID?
Bonner County, Idaho is in USDA Hardiness Zone 5b. The average last spring frost is May 5 and first fall frost is October 3.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Bonner County gardeners in Zone 5b organize planting dates, track what's growing, and never miss a planting window.
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