One of the best tools that you have as gardeners to help us figure out your gardening schedule is the 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 San Juan you can figure out when it's a good idea to plant watermelon by looking at the USDA zone info.

Planting Calendar for Watermelon

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

Watermelon require warm weather which means that you need to wait until it warms up after the last frost before you can plant them.

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

The last month that you can plant watermelon and expect a good harvest is probably September. You probably don't want to wait any later than that or else your watermelon may not have a chance to grow to maturity. Starting your watermelon indoors is a great way to get them started a few weeks earlier.

Last Frost Date

On average the last frost when the weather gets warmer is on February 15 in San Juan. It might get as low as 25°F during the coldest months of winter.

Always keep in mind that USDA zone info for San Juan is not always accurate and the actual date of last frost is different every year. Half of the time in San Juan there is a last frost after February 15 so make sure that you are ready to cover your watermelon in the event of one of those late frosts.

USDA Zone Info for San Juan

Here is the info for USDA Zone 9b.

Average Date of Last Frost (spring)	February 15
Average Date of First Frost (fall)	December 15
Lowest Expected Low	25°F
Highest Expected Low	30°F

This means that on a really cold year, the coldest it will get is 25°F. On most years you should be prepared to experience lows near 30°F.

Plants to Grow in San Juan

You may be interested in your other planting guides for San Juan.