Why does it snow? Why do lakes and ponds turn to ice?
In order for it to snow, there has to be enough moisture in the air, and it has to be below 32° F (0° C). If the air is warmer, it will rain or sleet instead. Snow is basically frozen water, but it freezes in the air in very tiny droplets, which makes crystals. There is a lot of air in snow, which means it is much lighter than water or ice. Sometimes there are bigger snowflakes because the tiny droplets stick together before they fall. If the air in the upper atmosphere is above 32° and the air nearer the ground is below 32°, the droplets may start as rain but freeze as they fall into the colder air. This makes sleet. Ice forms on the top of a lake when the water is less than 32° F. It only forms at the top because ice is lighter than water, so when water gets cold enough to turn to ice at 32° F, it floats to the top of the lake. Which is good for the fish who live under the ice! (Learn more about fish)
The links below take you outside the Power to Learn web site. Your use of the Internet will then be governed by the terms of usage and privacy practices of the particular website that you are accessing.
National Snow and Ice Data Center: All About Snow
Get answers to many more questions about snow and ice, including why snow is white, check out pictures of historic blizzards and interesting snow formations, and discover the definitions to many ice and snow-related terms at this site.
Why Ice Forms on Top of Lakes
USA Today explains why ice forms only at the top of lakes, with graphics showing how the cold water moves down until it becomes ice, and how the ice moves back to the top.
This site was designed by professors in Washington state to help elementary school students explore snow. It answers questions like where the moisture for snow comes from and offers activities to talk about snow in the classroom.
SnowSchool: Snow Science Lesson Plans
For teachers, SnowSchool offers lesson plans to do in the snow. Teach students about snow density and explore what substances melt snow most quickly.