As you have probably heard about a hundred times, no two snowflakes are alike. Although no two are alike, they all fall (LOL) into one of six categories. These categories are:
The Star category
The Dendrite category
The Columns category
The Column capped with plates category
The Plate category
The Needles category
The star looks like a star. They are the most common type of snowflakes. Large ones are very rare because they often get blown apart by the wind. The biggest one ever recorded was 8" by 12" in Siberia in 1971. The Dendrite also looks like a star. Dendrites form at -20° to -25° c. Plates have very little moisture. They form when there is little water. They form at a temperature of -10° to -20°c. Columns form when the air is dryer. Columns form at 15° to -25°c. They are generally smaller then star crystals. Column capped with plates forms when snow passes through a different temperature. A Needles snowflake is formed at -5° to -10°c. If you would like to see them you can go here http://www.teachervision.com/lesson-plans/lesson-3827.html