Giant Flakes
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Even though the ice crystals that make up snowflakes are hardly noticeable, snowflakes can grow to sizes that you could hardly miss. Hi I'm Dave Thurlow for the Weather Notebook.

The term "snowflake" refers to a clump of individual snow crystals, crystals that have stuck together as they fall. Snow crystals are typically two-hundredths to two tenths of an inch in diameter whereas snowflakes are about typically a quarter of an inch across but may be as large as one to two inches across. The big ones have hundreds and hundreds of individual crystals, the smaller flakes, just a few.

Snowflakes are most likely to form when air temperatures near the surface are around the freezing mark because snow crystals stick together best at these temperatures. At very cold temperatures, say around 10 to 20 below zero, snowflakes are uncommon, and if it does snow, the flakes are usually just single crystals.

For a snowflake to grow exceptionally large, conditions must be perfect. Besides having ideal temperatures for stickiness, the winds must be light or the biggest flakes will break up as they fall.

Some gargantuan snowflakes have been documented. The biggest one -15 inches across- fell in Montana. Another foot wide monster fell in Siberia where people watched it hurtle earthward. And a whole storm of teacup saucer sized flakes, about half a foot across, was reported in England.

You can observe the exquisite beauty of snowflakes and their component crystals by catching them on your coat sleeve. Bring a magnifying glass along for an extra close inspection; but, especially if it's near freezing, don't be surprised if a snowflake the size of frying pan falls and clocks you on the head.

See more about snowflakes at weathernotebook.org. Our show is a production of the Mount Washington Observatory.