We haven't had much snow for the first part of the winter, but in case you're wondering how snowflakes are formed, here you go.
A snowflake is formed when a water droplet freezes onto some particle in the atmosphere. That particle can be anything from pollen to dust in the clouds. From this an ice crystal is created. As the ice crystal falls to the ground, more water vapor freezes onto the primary crystal and the snowflake will grow in size. This is how the six arms of the snowflake are formed.
It's often said that no two snowflakes are the same. This is because each snowflake follows a slightly different path on it's journey through the atmosphere and finally to the ground. Along that path a number of different factors will come into play. Temperature is the biggest factor in that formation, although humidity also has an effect on the final look of the snowflake.
For example, when a snowflake forms at temperature in the middle 20s(Fahrenheit), the crystal will look long and needle-like. However, flakes that form at a temperature in the single digits(F) will tend to appear flat and plate-like.