How large can a snowflake get?

There technically isn’t a limit on the size of a snowflake but they’re very fragile. Even a small breeze can break up a large one. There have been many reports of snowflakes 5 – 15 cm (2 to 6 inches) in diameter. A snowflake 38 cm (15 inches) in diameter was observed at Fort Keogh, Montana, USA in 1887 although there isn’t anyone to corroborate the story.

How are snowflakes formed?

When air gets very cold the moisture in it condenses out into little water droplets. Close to the ground, the moisture condenses onto the grass in the form of frost or dew. In a cloud, water droplets condense around microscopic bits of dust or other particles floating around in the atmosphere.

In the winter the water droplets in a cloud start to slowly freeze and form into snowflake crystals. Other water droplets then condense and freeze on to these crystals making it bigger. Wind keeps it floating around in the cloud. The temperature and humidity around the snowflake varies slightly depending on where it is in the cloud. Even though the changes are small, they cause the crystals forming on the snowflake to have different shapes. These snowflakes are usually small have a lovely six-sided symmetry. When snowflakes collide and fuse they form “aggregated” snowflakes, which can get very large. Eventually the snowflake gets so heavy that it falls out of the cloud. The Montana snowflake must have been floating around in the cloud for quite a long time.