There are a number of ways to suggest rain, whether you concentrate on the storm itself, wet clouds that hang over a landscape, wonderfully subtle and gray values, lightning that accompanies a storm, the ripples on a pond, or the wet, reflective surfaces that rain creates. You may find that watercolor pencils work well for you for some effects but take concentration for others. That’s normal—just practice until all of the techniques come easily.
Rain striking a wet surface—a lake, a puddle or even a sidewalk—makes lovely rippled patterns. Watch for ways to suggest reflections, falling drops and splashes, but keep in mind that not all raindrops should look like a stereotypical droplet.