After a rain, the ground is softer and your mower can easily damage wet grass. It is best to wait until the lawn is dry to avoid rutting. If you must mow while the lawn is still wet, use a lower setting to avoid tearing the blades of grass. Mowing wet grass can also clump the grass clippings and make it difficult to discharge them from the mower. For these reasons, it is always best to wait until the lawn is completely dry before mowing.