snow: the white frozen precipitation that falls from the sky, lies on high mountains, and melts into water
Snow was a rare and startling sight across most of ancient Israel. It fell on the high northern peaks of Lebanon and Hermon, and only now and then on the hill country, so when the writers of the Bible reached for it the word carried a weight that a reader from a colder climate can easily miss.
The word does two jobs. Most plainly it names the real thing: snow that God sends down to the ground, the snow of Lebanon that never fails, meltwater filling the seasonal streams, the cold a household must be ready for. Alongside its frozen cousin (קֶרַח, ice and frost), it belongs to the ordinary weather God commands.
Far more often, though, snow appears as a picture of blinding whiteness. A hand or a face struck with disease turns "white as snow," and, most famously, guilt washed away leaves a person "whiter than snow." In a land where snow was bright, pure, and briefly seen, it made the perfect image for both sudden affliction and complete cleansing.