Changing Seasons
Do you have a favorite season? Spring's budding leaves, bright flowers, and warmer days bring new life. It's a great time to play outdoors, plant a garden, or watch a baseball game.
Hot summer days are great for swimming or playing at the beach. Sometimes a thunderstorm brings welcome relief from the heat.
Autumn days are crisp and cool. Tree leaves change to yellow, orange, red, and brown. Days get shorter.
The sun sets early in winter. Sledding, skating, and building snowmen are great fun on a cold winter day.
GET ACTIVE!
All living things need water. Water can exist as a solid, liquid, or gas.
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Pour liquid water into a glass. Use a washable china marker to mark the water level.
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Leave the glass in a sunny window for a day. Then check the water level. Has it changed?
Some water will evaporate. Evaporation changes liquid water into a gas, called water vapor. Water is constantly evaporating on Earth. Water vapor makes up the clouds in the sky.
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Refill the glass of water and move it to a waterproof table or counter. Add several ice cubes. Wait 20 minutes. What happens?
Water vapor isn't only in the clouds. It's also in the air around us. Water vapor outside the glass condensed as heat from the surrounding air and traveled to the cooler glass.
When it rains, water vapor in the clouds changes to droplets of water. Gravity pulls the droplets to the ground.
Water can fall from clouds as snow, hail, or sleet, as well as rain. Precipitation is the term scientists use for condensed water that falls from clouds to Earth. In nature, water is constantly falling, evaporating, and condensing again.
But wait! Not everyone experiences the seasons this way. While brisk December winds sweep across North Dakota, Los Angeles often gets warm, sunny days with temperatures over 75 degrees Fahrenheit (ºF). As New Englanders swelter from summer heat, Alaska can still have temperatures close to freezing.
Strangely enough, Earth is nearest the sun around January 3. Yet at that time, areas in the Northern Hemisphere have winter. Why?
If you shine a flashlight directly at a wall, you'll see a bright spot. Angle it, and you'll cover a broader area with a dimmer beam.
WORDS to KNOW
The same thing happens with Earth. As Earth orbits the sun, its axis stays tilted. During summer, the sun's rays strike the Northern Hemisphere directly. It receives more light and heat.
Also during summer, the tilt brings more areas within the sun's range. Thus, summer days are longer and brighter.
In winter, the Northern Hemisphere tilts away from the sun. Light falls indirectly, at an angle. Temperatures fall as days get shorter.
What happens in the Southern Hemisphere? Because of Earth's tilt, seasons there are reversed. December brings the start of summer to Australia. Winter starts in June.
Even in summer, it's cooler in Alaska than it is in Florida. Distance from the equator makes the difference. Polar regions always get the sun's rays at a slant, so they stay cold year round!
WORDS to KNOW
In contrast, direct sunlight brings more light and heat to areas near the equator. That means warmer weather all year round.
Prevailing winds, altitude (land height above sea level), nearness to lakes or oceans, and other factors also affect an area's weather. One tropical area may be a rain forest, while another is a desert.
Habitats are areas where living things make their homes. Temperature, rainfall, and other factors produce a variety of habitats. Each habitat plays an important part in the world of nature.
