Of all the smoothies I enjoy, I think this one sets the standard for refreshing. You can't beat the combination of watermelon and lemon for cooling a body down on a hot summer day. And lemon sherbet is the perfect ingredient to create even more cooling, as opposed to ice cream which can be a bit too creamy at times. Especially when the temperature is reaching into the 90's or even higher.
One little heads-up about watermelon. If you're tempted to buy seedless watermelon for this recipe, I wouldn't. I know it's convenient, not having to take the seeds out and all that, but the flavor just isn't there. I've tried them on several occasions and have gone back to picking out the seeds. The flavor difference is worth it to me.