Outdoor umbrellas are exposed to the harsh elements and are bound to get dirty at some point. Here’s how to clean an outdoor umbrella in four steps: 1. Remove debris: Using a brush, remove any dirt or leaves from the structure. 2. Scrub with soap: Dilute laundry detergent in warm water and gently scrub the umbrella surfaces. 3. Let rest: Allow the detergent to penetrate for around 30 minutes. 4. Rinse: Using a hose or bucket, thoroughly rinse your umbrella of all soapy residue.