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When to plant watermelons in zone 4a

In zone 4a, where the last spring frost typically comes around May 13, start watermelons indoors April 28 to May 12 and plant out June 2 to 16.

The zone 4a schedule for watermelons

Start seeds indoors
April 28 to May 12
Plant out
June 2 to 16
Sow outdoors
June 2 to 16
Soil warm enough (60°F), about
June 2
First harvest, roughly
August 1 to September 14

From the median frost dates of the NOAA stations assigned to the 739 ZIP codes in zone 4a, and the timing recommended by Cooperative Extension guides for watermelons.

Frost risk in zone 4a

Zones are based on winter cold, not on frost dates, so the last spring frost varies a lot within a zone. Across zone 4a, the typical last frost ranges from about May 6 in the earliest tenth of ZIP codes to May 24 in the latest tenth, and the first fall frost from September 20 to October 3. For a typical place in the zone:

  • April 30Risky: a later frost happens in 9 years out of 10
  • May 13Typical: frost after this date in half of years
  • May 27Safe: 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.

Enter your ZIP code

Watermelons in zone 4a cities

CityTypical last frostStart indoorsPlant out
Fargo, NDMay 10Apr 20 to May 4May 25 to Jun 8
Bismarck, NDMay 14Apr 23 to May 7May 28 to Jun 11
Grand Forks, NDMay 10Apr 24 to May 8May 29 to Jun 12

How to grow watermelonsAll zonesWatermelons in zone 3bWatermelons in zone 4bAbout zone 4a

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