Acid rain refers to acids, primarily nitric and sulfuric, formed in the atmosphere by a chemical reaction between water vapor and either sulfur dioxide (SO₂) or nitrogen oxides (NO_x). These acids linger in the atmosphere and eventually precipitate as rain or snow. Acid rain causes many problems, ranging from corrosion of marble statues and/or building fronts to the lowering of the pH in lakes and rivers, causing the water to be inhabitable by aquatic life.

Even retailer sites, such as Just Umbrellas, specialists in market umbrellas, include discussions of the damage caused by acid rain. According to their site, market umbrellas would not need to be repaired as often if not for the effects of acid rain.