Rain may wash away some surface dust, but it also leaves behind something worse—mineral deposits. In San Jose, where water is rich in calcium and magnesium, a rainstorm can create hard water stains on your solar panels. After a storm, panels often look dirtier than before, with streaks and spots that block sunlight. Bird droppings and pollen also mix with rain, forming a film that bakes onto the panel surface when the sun comes back out. That’s why many San Jose solar professionals recommend a post-rain cleaning, especially during stormy spring months. Homes in East Foothills and Cambrian Park, where tree coverage is heavy, tend to suffer the most after rainfall. If you notice haze, dullness, or a dip in system output after a storm, it’s time for a professional cleaning. Clean solar panels after rainfall help restore maximum efficiency and protect your system from long-term damage caused by deposits.