For hundreds of years, people have attempted to forecast the weather based on the conditions in the sky. Even Jesus himself spoke of interpreting the weather by the color of the sky in Matthew 16:2-3. However, the best weather indicators in the sky are clouds because each type of cloud forms in a different way and brings its own kind of weather.
Clouds are made up of water, and they form when water vapor condenses around particles of dust. Clouds are classified by how high they form and their appearance. The LIFEPAC® science curriculum for 7th grade from Alpha Omega Publications® states there are three basic types of clouds - cirrus, stratus, and cumulus.
Cirrus clouds are high and thin (they look like a horse's mane) and indicate that light rain and snow are possible within one to two days. Stratus clouds are layered and look like a blanket as they cover most of the sky. Depending how high they form they indicate either colder weather or immediate rain, drizzle, and snow. Cumulus clouds are low and puffy clouds that look like balls of cotton as they rise like towers in the sky. They normally signal fair weather except when they build in the middle or high part of the atmosphere. At that level, cumulus clouds become cumulonimbus clouds and indicate severe weather with hail, damaging winds, or tornados from rising and sinking air currents.
Although studying clouds outside is much more fun, you can also motivate your child to learn more about clouds in your science class with the following experiments:
Cloud in a Jar
1 gallon glass jar
Black construction paper
Plastic freezer bag
Fill plastic bag with enough ice so it will cover the neck of the jar, but not fall through. Set aside. Cover ¾ of the outside of the glass jar with black construction paper and hold in place with tape to make your "cloud" more visible. Pour 1-2" of warm water into the jar. Light a stick match and hold it just inside the top of the jar for a few seconds before dropping it into the water. Place the bagged ice on top of the jar immediately.
What you should observe:
A cloud will form between the water in the jar and the bagged ice. As warm air rises, it expands and is cooled. Clouds form when tiny invisible drops of moisture in the air (water vapor) become visible water drops. When the water vapor is cooled below the dew point, it becomes visible. This same process is what happens on a cold day when you see your breath.
1 quart glass canning jar
Cover the bottom of the jar with two inches of very hot water. Place your plate tightly on top of the jar and wait 3-4 minutes before the next step. Place as many ice cubes as possible on the plate.
What you should observe:
Droplets of "rain" will form because the cold plate causes the moisture in the warm air inside the jar to condense. In the sky, the same thing happens as warm, moist air rises and meets colder air higher in the atmosphere. The condensing water vapor eventually grows heavy and falls back down to the earth as rain.
After studying clouds, your child won't need to watch the weather forecast on TV any longer to know what he should wear each day. He can simply go outside, look up, and watch the clouds.