They always occur in showers and are often accompanied by snow flakes or rain drops, when the surface temperature is around zero Celsius. Snow grains are minute, white and opaque grains of ice. When they hit hard ground, they do not bounce or shatter. They usually fall in very small quantities, and never in the form of a shower. Ice pellets are tiny, translucent frozen raindrops or snowflakes, or snow encased in ice, which bounce and make a sound on contact with the ground.
Ice crystals are tiny sprinkles that sparkle in the sunshine like diamond dust and hang in the air.
Hail is precipitation in the form of lumps of ice, larger than ice pellets, usually the size of peas or cherries but sometimes as large as oranges. Often associated with thunderstorms, hail forms when drafts carry raindrops upward into extremely cold regions of the atmosphere. There, the drops freeze and merge into lumps of ice. When the lumps become too heavy to be supported by the updraft, they fall to the ground at high speeds. The probability of precipitation is a subjective estimate of the chance of precipitation.