When to plant Watermelon in Weld County County,
In Zone 5b (Weld County County), direct-sow Watermelon between May 9 and May 30 for spring, after the May 2 last-frost mark.
When to Plant Watermelon in Weld County, CO
Your June planting checklist for Weld County, Colorado
Your garden in Weld County, Colorado is working on a schedule, even when you're not. Here's where you should be this June.
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Start watermelon under lights
Your window is short. These crops want several weeks of indoor growth before they go outside.
Get ahead of July
- First harvests: watermelon
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.
Weld County, Colorado is in USDA Zone 5b. The average last spring frost is May 2 and the first fall frost is October 7, giving you a growing season of approximately 158 days.
At an elevation of 6,992 feet, Weld County receives approximately 18.8 inches of rainfall annually with predominantly loam soil. Summer highs average 87°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.
Weld County Soil Profile
Soil Type
Loam
Soil pH
6.6-8.1
Drainage
Well Drained
Watermelon 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.
Soil Compatibility in Weld County
How your county's soil matches Watermelon's growing requirements.
Soil pH
Your soil pH (6.6–8.1) overlaps with Watermelon's range (6.0–7.5), though not a perfect match.
Soil Texture
The loam soil in Weld County is excellent for Watermelon — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.2%). Annual compost additions will help Watermelon.
How to Plant Watermelon
Succession Planting Watermelon
Sow every 8 weeks. Last sowing by Jun 29 to harvest before frost.
Watermelon Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Watermelon
Watermelon needs approximately 1.5 inches of water per week (6.5" per month). Here's how your county's rainfall compares month by month.
| Month | Watermelon Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.4" | 0" | ❄️ Dormant |
| Feb | — | 1" | 0" | ❄️ Dormant |
| Mar | — | 1.5" | 0" | ❄️ Dormant |
| Apr | — | 2.1" | 0" | ❄️ Dormant |
| May | 6.5" | 2.3" | 4.2" | 🚿 Regular watering |
| Jun | 6.5" | 1.4" | 5.1" | 🚿 Regular watering |
| Jul | 6.5" | 1.7" | 4.8" | 🚿 Regular watering |
| Aug | 6.5" | 1.8" | 4.7" | 🚿 Regular watering |
| Sep | 6.5" | 1.7" | 4.8" | 🚿 Regular watering |
| Oct | 6.5" | 1.7" | 4.8" | 🚿 Regular watering |
| Nov | — | 1.2" | 0" | ❄️ Dormant |
| Dec | — | 1.1" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Weld County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Watermelon Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
Watermelon Planting Timeline — Weld County, CO
Watermelon Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 28 | Mar 28 – Apr 11 |
| Transplant Outdoors | May 16 | May 16 – May 30 |
| Direct Sow | May 9 | May 9 – May 30 |
| Harvest | July 25 | Jul 25 – Sep 12 |
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 | — |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1.5"/week · 2-3 times/week
📅 Days to Maturity
70–100 days
🧪 Soil pH
Needs 6–7.5 · Your soil: acceptable
🗺️ USDA Zone
Zone 5b
📆 Growing Season
158 days in Weld County
Growing Tips for Watermelon in Weld County
Direct sow Watermelon outdoors after May 02 in Weld County when soil has warmed and frost danger has passed.
Common pests for Watermelon in this region include squash vine borer and cucumber beetles. Use row covers early in the season and inspect plants weekly.
Weld County receives only 19" of rain annually. Watermelon needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
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.
Recommended Watermelon Varieties for Weld County
Compact, early melons for shorter seasons
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 Weld County, CO?
Weld County is in Zone 5b with an average last frost of May 2. Plan your Watermelon planting based on this frost date — see the calendar above for exact timing.
What planting zone is Weld County, CO?
Weld County, Colorado is in USDA Hardiness Zone 5b. The average last spring frost is May 2 and first fall frost is October 7.
When should I plant Watermelon in Weld County, ?
In Weld County, , plant Watermelon after the last frost (around May 2) and before the first frost (around October 7). Best results when soil holds above 50°F.
What growing zone is Weld County, for Watermelon?
Weld County sits in USDA Zone 5b. Watermelon grows reliably in zones 4a through 11b, so it's a good fit here.
Can Watermelon grow in Weld County's climate?
Yes — Watermelon grows well in Weld County's temperate climate. Weld County averages a 158-day frost-free season, with last frost around May 2 and first frost around October 7.
Your Weld County Garden Planner — Free
A 22-page printable planner built for Weld County (Zone 5b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.