Describe rain hitting a windscreen by describing its effect. For example, you might state: the constant patter of raindrops on the windscreen during the storm was the first sign of the coming spring.
Describe rain hitting the windscreen with evocative language. For example, you might state: the raindrops splashed and divided against the windscreen, reflecting the sun's light into a thousand glittering prisms, rolling and tumbling under the relentless caress of the wind.
Describe rain hitting the windscreen by giving it human characteristics. For example, you might state: the storm broke; and the first wave of splattering raindrops began their suicidal descent from the clouds, diving into the windscreen below.