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Snowstorms happen when a mass of very cold air moves away from the polar regions. When it collides with a warm air mass, the warm air rises quickly and the cold air cuts underneath it. This causes a huge cloud bank to form, leading to heavy snowfall. Snow will only fall from the cloud if the temperature of the air between the bottom of the cloud and the ground is below 40ºF. A higher temperature will cause the snowflakes to melt as they fall through the air, turning them into rain or sleet.

Snowflakes form when ice crystals collide in a cloud and stick together. Every snowflake has six sides, and no two snowflakes that fall are exactly alike. Their varying shapes are a result of the different weather conditions in which they are produced. Needle and rod shapes are formed by cold air, while warmer air results to more complicated patterns.

Some scientists think that cold winters are caused in part by changes in ocean surface temperatures. As winds move over continents, they are influenced by complex interactions between the oceans and the atmosphere. El Nino, a warm ocean current, is also pointed to as the cause of large-scale oceanic and atmospheric changes.

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