Our window cleaning system is designed to clean windows all year round in all weather types, even when it's raining, so we're able to guarantee the same streak-free quality clean 12 months of the year. The fact is rain water is purified soft water containing no impurities and so is the exact same form of water as we use. This means whenever we clean your windows in the rain the quality of the clean is unaffected. Soft water pulls dirt off windows and into the water droplets via a process called osmosis. It is dirt carried in the wind that makes windows unclean.
Hard Water is the opposite type of water to purified soft water. We will only ever use purified soft water to clean your windows. Hard water is what comes out of everyone's taps at home and contains many impurities such as calcium gathered from underground. If we used tap water to clean your windows it would leave streaks, which are the impurities such as calcium left on the glass after the water has evaporated. Also likewise, if we used soapy water to clean your windows but didn't dry your windows afterwards it would leave streaks too, which again are the impurities of the soap left on the glass after the water has evaporated.