No, it's not a myth: No two snowflakes are ever alike

Snowflakes on an evergreen bush. Chronicle photo HOLLY LUNDH

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DeKALB - Millions or even billions of snowflakes fall to the earth every winter. But each of those flakes is different. "No two snowflakes are ever exactly alike," said Gilbert Sebenste, Northern Illinois University staff meteorologist. "At the center of snowflakes are pieces of debris or dust, and since the sizes of particles vary, the snowflakes vary." Tiny dust particles attract moisture in the air. As the moisture cools, it forms ice crystals that extend outward, creating diversely shaped flakes. "If you are outside and catch some flakes on your gloves, they might appear similar or even identical," Sebenste said. "But if you look at them under a microscope, you will see each is different." The size of snowflakes depends on the temperatures they experience on their way to the ground. For nice, large flakes, the ground level usually needs to be around 32 degrees and cloud level between 10 and 15 degrees, Sebenste said. When the air at ground level is cooler than the air at cloud level, the moisture falls as sleet. Under such conditions, the moisture collects into water drops but then quickly cools into ice because it drops too quickly to congeal into snow. The moisture turns into freezing rain when the air is clear of dust particles because the moisture has nothing to which to cling. Sebenste said he saw freezing rain a few years ago in this area. "None of the forecasters got that forecast right," he said with a laugh. "The air is rarely clear enough for freezing rain." Although Sebenste doesn't expect any freezing rain this season, the meteorologist predicts the DeKalb area will get about 35 inches of snow this winter. The heaviest snowfalls usually come in January and February, although DeKalb received 25 inches of snow in March 1912. "I hope that doesn't happen this year," Sebenste said. Renee Messacar can be reached at rmessacar@ pulitzer.net.