One of the first steps you take when you are estimating your gardening schedule is find your USDA Zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

In Spearfish you can figure out when it's possible to plant watermelon by using the USDA zone info.

Planting Calendar for Watermelon

Frost tolerance for watermelon:	Not tolerant of frost.
When to plant:	After the last frost has passed.

It's not a good idea to plant watermelon until after all chance of frost has passed because they are not cold tolerant.

The earliest that you can plant watermelon in Spearfish is April. However, you really should wait until May if you don't want to take any chances.

The last month that you can plant watermelon and expect a good harvest is probably August. If you wait any later than that and your watermelon may not have a chance to fully mature. If you are starting your watermelon indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

In Spearfish the average date of last frost happens on April 15. In the coldest months of winter you can expect an average low temperature of -20°F.

Since the USDA zone info for Spearfish is an average the actual date of last frost can change quite a bit from year to year. Half of the time in Spearfish you get a frost after April 15 so just be sure to be ready to cover your watermelon if you have a late frost.

USDA Zone Info for Spearfish

Here is the info for USDA Zone 5a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-20°F
Highest Expected Low	-15°F

This means that on a really cold year, the coldest it will get is -20°F. On most years you should be prepared to experience lows near -15°F.

Plants to Grow in Spearfish

You may be interested in your other planting guides for Spearfish.