“How can there be flying rivers of water?”
Rain is usually delivered through means of water vapor held in clouds dissipating. By coastal areas, water can build up in the atmosphere from evaporation from the ocean and then move landside where it can hit elevation, become colder, and then burst and create serious downpours. These Atmospheric Rivers can give up words of over 50% of California’s annual rainwater.
Image credit http://www.frontiersin.org