So since it was raining today and I’ve had a few requests recently to reschedule due to rain, I thought I’d mention the truth about the rain. It is a very common thought that rain water will mess up the windows after they have been cleaned. However the truth is that rain is considered pure water. The TDS (total dissolved solids) reading is so low that it will not leave any marks on clean windows. What does make spots is dirt or dust! When dust and dirt settle on the glass over time it is dispersed on the glass when water hits it leaving water spots. We always include a rain guarantee in the case of a windy rain storm where dirt and dust get blown across the glass mixing with rain and making it spotty. But the truth is that rain itself will not make your windows dirty.