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When to Plant Watermelon in Pembina County, ND

Pembina County, North Dakota Zone 4a May

Pembina County, North Dakota gardeners: here's your May plan

May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Pembina County, North Dakota.

Avg. last frost May 15
Avg. first frost September 28
Soil temp (4") 49°F
Watering Moderate
Pest pressure Low
Daylight 15 hrs
  1. Put watermelon seeds straight in the ground

    Rake a smooth bed, make a shallow furrow, drop seeds at the spacing on the packet, water gently, walk away.

A few tasks this May that'll pay off in June
  • Transplants going out: watermelon
  • Starting indoors: watermelon

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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.

Pembina County, North Dakota is in USDA Zone 4a. The average last spring frost is May 15 and the first fall frost is September 28, giving you a growing season of approximately 136 days.

At an elevation of 958 feet, Pembina County receives approximately 26.5 inches of rainfall annually with predominantly loam soil. Summer highs average 79°F, so choose short-season varieties of Watermelon to ensure they mature before fall.

Pembina County, ND (Zone 4a) Short season
136 days
Last Spring Frost May 15
136 growing days
First Fall Frost September 28

Pembina County Soil Profile

Soil Type

Loam

Soil pH

6.6-7.3

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 30 Transplant: Jun 1 🍅 Harvest: Aug 10 – Sep 28
Recommended (50%) ✗ May not fit
Start indoors: Apr 3 Transplant: Jun 5 🍅 Harvest: Aug 14 – Oct 2
Safe Start (90%) ✗ May not fit
Start indoors: Apr 18 Transplant: Jun 20 🍅 Harvest: Aug 29 – Oct 17

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 Pembina County

How your county's soil matches Watermelon's growing requirements.

Soil pH

Your soil pH (6.6–7.3) is within Watermelon's preferred range (6.0–7.5).

Soil Texture

The loam soil in Pembina County is excellent for Watermelon — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is excellent (4.2%) — Watermelon will thrive.

How to Plant Watermelon

1"
Planting Depth
30"
Between Plants
42"
Between Rows

Succession Planting Watermelon

2
successive plantings in your 136-day season

Sow every 8 weeks. Last sowing by Jun 20 to harvest before frost.

Plant Water Budget

Plant needs
1.5″/week
Rainfall provides
0.8″/week
You supply
0.7″/week
Watering frequency 1-2 times/week
Season total 825 gal / 100 sq ft

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 0.7" 0" ❄️ Dormant
Feb 1" 0" ❄️ Dormant
Mar 1.7" 0" ❄️ Dormant
Apr 2.6" 0" ❄️ Dormant
May 6.5" 3.6" 2.9" 💧 Light watering
Jun 6.5" 4.7" 1.8" 💧 Light watering
Jul 6.5" 3.2" 3.3" 🚿 Regular watering
Aug 6.5" 3.4" 3.1" 💧 Light watering
Sep 6.5" 2.7" 3.8" 🚿 Regular watering
Oct 1.4" 0" ❄️ Dormant
Nov 0.8" 0" ❄️ Dormant
Dec 0.6" 0" ❄️ Dormant

Water needs are for active growing months only (May–Sep in Pembina 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 needs ~786 GDD — county provides 1,258 GDD Excellent fit

Watermelon Planting Timeline — Pembina County, ND

Watermelon Planting Calendar

Activity When Date Range
Start Indoors April 3 Apr 3 – Apr 17
Transplant Outdoors June 5 Jun 5 – Jun 19
Direct Sow May 29 May 29 – Jun 19
Harvest August 14 Aug 14 – Oct 2

Plant 1" deep · 30" apart · Rows 42" apart

Month-by-Month Timeline

MonthActivities
January
February
March
April Start Indoors
May Direct Sow
June Transplant Outdoors Direct Sow
July
August Harvest
September Harvest
October Harvest
November
December

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1.5"/week · 1-2 times/week

📅 Days to Maturity

70–100 days

🧪 Soil pH

Needs 6–7.5 · Your soil: ideal

🗺️ USDA Zone

Zone 4a

📆 Growing Season

136 days in Pembina County

Growing Tips for Watermelon in Pembina County

Direct sow Watermelon outdoors after May 15 in Pembina 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.

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 Pembina County

Compact, early melons for shorter seasons

Sugar Baby (75d) Blacktail Mountain (70d) Golden Midget (70d)

Companion Planting

Good Companions

Avoid Planting Near

  • Potatoes

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Watermelon in Pembina County, ND?

Pembina County is in Zone 4a with an average last frost of May 15. Plan your Watermelon planting based on this frost date — see the calendar above for exact timing.

What planting zone is Pembina County, ND?

Pembina County, North Dakota is in USDA Hardiness Zone 4a. The average last spring frost is May 15 and first fall frost is September 28.

🌱

Your Pembina County Garden Planner — Free

A 24-page printable planner built for Pembina County (Zone 4a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

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Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Pembina County, ND. Local conditions may vary. Last updated: May 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.