Using frozen watermelon ensures a cold and creamy smoothie that blends easily in the blender. Plan to freeze the watermelon at least 6 hours before you want to make the smoothie.
Blend, starting on low and working up to high, using the stick that came with the blender (if you have one) to get it going.
Serve immediately.
Notes
To freeze watermelon: Place the watermelon cubes into a zip top freezer bag and lay flat in one layer in the freezer to freeze. This will avoid them all freezing together in one large clump. Do this at least 6 hours before you plan to make the smoothie.
Use seedless watermelon to make your life easier and avoid having to pick out seeds.
Use a nondairy yogurt if you prefer.
Use plain yogurt if you prefer and sweeten to taste with maple syrup or honey.
You can freeze the blended mixture in freezer pop molds to make homemade popsicles for the kids.
Serve the smoothie in a small cup, in a cup with a straw, or in a reusable pouch.