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ALEX POTEMKIN/GETTY IMAGES
STANDARDS
NGSS: Core Idea: PS1.A, ESS2.D, ESS3.D
CCSS: Literacy in Science: 7
TEKS: 6.2B, 7.2B, 8.2B, 8.10A, ESS.11F
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Snow Day!
Sometimes winter snowstorms lead to a surprise day off from school. But will snow days soon become a thing of the past?
AS YOU READ, THINK ABOUT how a changing climate could affect winter weather.
For many students across the U.S., winter brings the possibility of a snow day! Heavy snowfall can cover sidewalks and make roads dangerous, forcing schools to close. Students then get to stay home to sip hot chocolate, go sledding, and have snowball fights!
For snow to fall, local conditions must be just right. Snow forms in clouds when temperatures hit or dip below 0°C (32°F)—water’s freezing point. As droplets of water turn from liquid to solid, their molecules arrange into a repeating pattern, creating six-sided crystals. But snowflakes won’t start piling up unless temperatures near the ground are similarly cold. If it’s too warm, the precipitation will ultimately fall as sleet or freezing rain.
For many students across the U.S., winter could bring a snow day! Heavy snowfall can cover sidewalks and make roads dangerous. That forces schools to close. Then students get to stay home. They can sip hot chocolate, go sledding, and have snowball fights!
Local conditions must be just right for snow to fall. Snow forms in clouds at or below 0°C (32°F). That’s water’s freezing point. As droplets of water turn from liquid to solid, their molecules arrange into a repeating pattern. This creates six-sided crystals. But temperatures near the ground must also be cold or snowflakes won’t pile up. If it’s too warm, sleet or freezing rain will fall instead.
SHUTTERSTOCK.COM
The largest snowflake ever recorded was 15 inches across. It was made of many ice crystals stuck together and was measured in 1887. The largest single crystal, 0.4 inch wide, fell in Canada in 2003.
Climate change could also affect the chances of having a snow day. Brian Brettschneider, a climate scientist with the National Weather Service in Alaska, has analyzed data on snowfall trends. His results show that as temperatures have climbed over the past 50 years, annual snowfall has declined by an average of 20 percent across the contiguous U.S. (the 48 states besides Alaska and Hawaii). And even when snow does pile up, some schools are opting for students to learn remotely online instead of closing completely. So if you’re lucky enough to get a snow day this winter, make the most of it!
Climate change could also affect the chances of having a snow day. Brian Brettschneider is a climate scientist with the National Weather Service in Alaska. He has studied data on snowfall trends. His results show a change over the past 50 years. As temperatures have climbed, annual snowfall has decreased by an average of 20 percent across the contiguous U.S. That means the 48 states besides Alaska and Hawaii. And even when snow does pile up, some schools don’t close completely. Instead, their students learn remotely online. So if you’re lucky enough to get a snow day this winter, make the most of it!
Snowfall varies greatly across the U.S. This bar graph shows which states receive the greatest amount of snow each year.
SOURCE: NATIONAL CENTERS FOR ENVIRONMENTAL INFORMATION
DIG INTO THE DATA: About how many times as much snow falls annually in New Hampshire as in Utah?
Here’s how storms create falling snowflakes.
DIAGRAM BY KATE FRANCIS
Warm air rises into the atmosphere. The air carries water that has evaporated, or turned from a liquid into a gas.
As the moist air cools, water condenses back into a liquid—clinging to tiny dust particles in the air and forming clouds. If temperatures are below freezing, the droplets form ice crystals.
As more water freezes to the crystals, they grow into snowflakes.
When the snowflakes become heavy enough, they fall to the ground.
DIG INTO THE DATA: Would snowflakes form if the temperature in a cloud was 35°F?
The map below shows how the amount of snowfall received during the winter of 2023-24 compared with the average snowfall over the previous 15 years.
SOURCES: GREG FALL / TIMES UNION / NOAA OFFICE OF WATER PREDICTION, MARCH 2024
JIM MCMAHON/MAPMAN ® (MAP)
DIG INTO THE DATA: Last winter, which was greater: the total area receiving more snow than usual or less than usual?
For decades, kids around the country have performed good-luck rituals in hopes of getting a snow day. Here are a few.
Taping coins to the window
Flushing an ice cube down the toilet
Sleeping with a spoon under a pillow or in the freezer
DRAGON CLAWS/ALAMY STOCK PHOTO
Setting white crayons on the windowsill
Wearing mismatched socks
Putting pajamas on inside out
DIG INTO THE DATA: Have you ever tried out any of these snow day superstitions?