Are All Snowflakes Really Different? The Science of Winter

For most in the Northern Hemisphere, winter is a time for building snowmen, skiing, and hoping for a snow day. Although many of us are counting down the days until holiday break, there is still time to investigate a few winter science questions! Grab some cocoa and your favorite blanket, and investigate winter from the comfort of somewhere warm.

Photo of children playing in snow


Why do we get the flu in the winter?

A runny nose, chills, a fever – winter is here, and so is flu season. Although the flu virus is around all year, why do most cases occur during these cold, dark months? Scientists are still working on the answer, but they have a few hypotheses:

  • We spend more time inside in the winter. The flu virus travels through tiny drops of water in the air, like those released when we cough or sneeze. Since we are locked inside for most of the winter, it becomes hard to escape those flu-carrying droplets if someone is sick. The virus is trapped indoors, more people breathe it in, and more get sick!
  • Winter weakens our immune system. With less direct sunlight and colder temperatures in the winter, our bodies produce less Vitamin D and melatonin, which may weaken our immune system and make us more likely to catch the flu.
  • The flu virus travels farthest in the cold. In 2007, Dr. Peter Palese performed an experiment that showed how the flu travels much better in the cold, dry air of winter. In the summer, when the air is humid, the droplets containing the flu virus absorb water, become large and heavy, and fall to the ground. Meanwhile, in the winter, the air can dry out the droplets, making them smaller, lighter, and able to be blown by the wind – blown far enough, in fact, for a new victim to inhale them and get sick.


How do birds stay warm in the winter?

When the temperature falls, we can layer hats, coats, and scarves. Birds, however, don’t have the same luxury. While many species fly to warm, southern regions, a handful stick around to brave the cold, but how do they survive?

Photo of bird resting in snow

It all starts with feathers. According to Peter Marra, head of the Smithsonian Migratory Bird Center at the National Zoo, “Birds’ feathers provide remarkable insulation against the cold, and the oil that coats feathers also provides waterproofing, which is important since the only thing worse than being cold, is being cold and wet.” In his interview with Smithsonian Science, Marra also shared that many small birds gather at night and crowd together to share body heat.

Birds’ legs are also designed to stay warm! “Veins and arteries in the leg are close to each other,” Marra explained, “and as warm blood [travels to the legs], it heats up the cold blood returning to the body. It’s brilliant!”

You can read more from Peter Marra in his interview with Smithsonian Science!


Are all snowflakes really different?

They say that no two snowflakes are alike, but with trillions falling every year, is that even possible? First, it helps to know more about how snowflakes are made.

When the air is colder than 0° Celsius (or 32° Fahrenheit), snow crystals begin to form from water vapor high in the atmosphere. As more water vapor condenses and freezes on these crystals, they form the beautiful shapes and branches we call snowflake!

Surely, though, some snowflakes have to be exactly the same, right? Not at all!

Although snowflakes are all the same on an atomic level (they are all made of the same hydrogen and oxygen atoms), it is almost impossible for two snowflakes to form complicated designs in exactly the same way. While snowflakes can be sorted into about forty categories, scientists estimate that there are up to 10158 snowflake possibilities. (That’s 1070 times more designs than there are atoms in the universe!)

While some may love winter, there’s no need to worry for those who don’t: Spring is just around the corner. 

Editors note: Have your students create DIY snowflakes with this hands-on activity from Carolina Biological


  • Elert, E. (2013, January 17). FYI: Why Is There A Winter Flu Season? Retrieved July 17, 2015.

  • Fessenden, M. (2014, December 30). Snowflakes All Fall In One of 35 Different Shapes. Retrieved July 22, 2015.

  • Gibbons, J. (2015, January 30). Keeping Warm in Winter is for the Birds. Retrieved July 22, 2015.

  • Libbrecht, K. (n.d.). Snowflakes - No Two Alike? Retrieved July 22, 2015.

About the Author

Alexis Stempien
SSEC Science Writing Intern, Summer 2015

Alexis specializes in writing, video, and social media. A senior at the University of Michigan, she studies Biopsychology, Cognition, and Neuroscience with a Minor in Writing. Outside of the classroom, she enjoys producing videos for her YouTube channel These Neon Hearts, playing mellophone in the Michigan Marching Band, and enthusiastically explaining science news to everyone around her.