Snow is cold because it is formed by water crystals combining, a process that can only occur when the temperature falls to 35 degrees Fahrenheit or below. When the temperature is over 35 degrees Fahrenheit, the precipitation is made of sleet or rain.
The colder the temperature, the dryer and fluffier the snow is due to the smaller sized snowflakes. When temperatures are higher, the outside of the snow crystals begin to melt and the snow comes down in wetter, heavier and larger flakes. The crystals connect together differently depending on the temperature and humidity, leading to the unique shapes found among snowflakes.