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When to plant watermelons in zone 4b

In zone 4b, where the last spring frost typically comes around May 8, start watermelons indoors April 23 to May 7 and plant out May 28 to June 11.

The zone 4b schedule for watermelons

Start seeds indoors
April 23 to May 7
Plant out
May 28 to June 11
Sow outdoors
May 28 to June 11
Soil warm enough (60°F), about
May 28
First harvest, roughly
July 27 to September 9

From the median frost dates of the NOAA stations assigned to the 1,164 ZIP codes in zone 4b, and the timing recommended by Cooperative Extension guides for watermelons.

Frost risk in zone 4b

Zones are based on winter cold, not on frost dates, so the last spring frost varies a lot within a zone. Across zone 4b, the typical last frost ranges from about May 1 in the earliest tenth of ZIP codes to May 25 in the latest tenth, and the first fall frost from September 22 to October 8. For a typical place in the zone:

  • April 26Risky: a later frost happens in 9 years out of 10
  • May 8Typical: frost after this date in half of years
  • May 22Safe: 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 4b cities

CityTypical last frostStart indoorsPlant out
Rochester, MNApr 30Apr 18 to May 2May 23 to Jun 6
Duluth, MNMay 6May 17 to 31Jun 21 to Jul 5
Lakeville, MNMay 2Apr 19 to May 3May 24 to Jun 7
St. Cloud, MNMay 7Apr 22 to May 6May 27 to Jun 10
Eau Claire, WIMay 8Apr 19 to May 3May 24 to Jun 7
Great Falls, MTMay 19May 15 to 29Jun 19 to Jul 3

How to grow watermelonsAll zonesWatermelons in zone 4aWatermelons in zone 5aAbout zone 4b

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