When to plant watermelons in zone 5b
In zone 5b, where the last spring frost typically comes around May 1, start watermelons indoors April 18 to May 2 and plant out May 23 to June 6.
The zone 5b schedule for watermelons
- Start seeds indoors
- April 18 to May 2
- Plant out
- May 23 to June 6
- Sow outdoors
- May 23 to June 6
- Soil warm enough (60°F), about
- May 23
- First harvest, roughly
- July 22 to September 4
From the median frost dates of the NOAA stations assigned to the 2,546 ZIP codes in zone 5b, and the timing recommended by Cooperative Extension guides for watermelons.
Frost risk in zone 5b
Zones are based on winter cold, not on frost dates, so the last spring frost varies a lot within a zone. Across zone 5b, the typical last frost ranges from about April 21 in the earliest tenth of ZIP codes to May 18 in the latest tenth, and the first fall frost from September 30 to October 19. For a typical place in the zone:
- April 18Risky: a later frost happens in 9 years out of 10
- May 1Typical: frost after this date in half of years
- May 16Safe: a later frost only 1 year in 10
Watermelons are killed by frost, so if you want to be safe, plant out after the safe date rather than the typical one, or be ready to cover plants on a cold night.
Your dates for watermelons
Set your ZIP code at the top of the page and we will work out when to plant watermelons where you live, from the frost records of the nearest NOAA weather station. Your ZIP code is remembered on this device only.
Watermelons in zone 5b cities
| City | Typical last frost | Start indoors | Plant out |
|---|---|---|---|
| Milwaukee, WI | Apr 19 | Apr 20 to May 4 | May 25 to Jun 8 |
| Madison, WI | May 1 | Apr 17 to May 1 | May 22 to Jun 5 |
| Des Moines, IA | Apr 18 | Apr 5 to 19 | May 10 to 24 |
| Aurora, IL | Apr 19 | Apr 10 to 24 | May 15 to 29 |
| Fort Collins, CO | May 2 | Apr 18 to May 2 | May 23 to Jun 6 |
| Naperville, IL | Apr 19 | Apr 10 to 24 | May 15 to 29 |
| Rockford, IL | Apr 24 | Apr 10 to 24 | May 15 to 29 |
| Elgin, IL | Apr 26 | Apr 13 to 27 | May 18 to Jun 1 |
| Greeley, CO | May 2 | Apr 13 to 27 | May 18 to Jun 1 |
| Green Bay, WI | Apr 30 | Apr 21 to May 5 | May 26 to Jun 9 |
| Davenport, IA | Apr 19 | Apr 7 to 21 | May 12 to 26 |
| Longmont, CO | May 6 | Apr 20 to May 4 | May 25 to Jun 8 |
How to grow watermelonsAll zonesWatermelons in zone 5aWatermelons in zone 6aAbout zone 5b
Sources
- Growing Watermelon in the Home Garden · Iowa State University Extension and Outreach
- How to Grow Watermelon in Your Garden · Utah State University Extension
- Watermelon (HGIC factsheet) · Clemson Cooperative Extension Home & Garden Information Center
- Citrullus lanatus (Watermelon) · NC State Extension Gardener Plant Toolbox
- Florida Vegetable Gardening Guide (SP103/VH021) · University of Florida IFAS Extension
- Vegetable Planting Calendar for Maricopa County (AZ1005) · University of Arizona Cooperative Extension