Snow is made of ice crystals. Actually, a snowflake is not much different than a raindrop. They're both made of water. The difference is that a snowflake forms in air that's below freezing and remains in generally freezing air all the way to the ground. Raindrops may or may not form in freezing conditions. Some raindrops begin and end as raindrops. Others start out as snowflakes, but melt before hitting the ground .