Weather and Seasons

Weather and Seasons The Earth is divided into two halves – the Northern Hemisphere and the Southern Hemisphere. As the Earth revolves around the Sun, sunlight hits one hemisphere more directly than the other. This causes us to experience seasons. In June, for example, the Northern Hemisphere is tilted toward the Sun and is in summer. The Southern Hemisphere is tilted away from the Sun and is in winter. The United States is in the Northern Hemisphere. In June, it is summer. New Zealand is in the Southern Hemisphere. In June, it is winter. Go Online! Observe how the Earth’s tilt and revolution around the Sun cause us to experience seasons on the NGScience website. QuickCode: R4S7 educatio nd Seaso d Seaso ed into two halv nto two hal sphere and the ere and the As the Earth rev e Earth re ht hits one hemis s one hemis other. This cause er. This caus s. In June, for exa . In June, for ex sphere is tilted to ere is tilted to mmer. The South The Sout om the Sun and he Sun and land is in the South and is in the Sout ere. In June, it is wi re. In June, it is w

Summer

Northern Hemisphere

Winter

66

Southern Hemisphere

Summer is the hottest season, occurring between spring and fall. Summer is the season with the most hours of daylight. It has the earliest sunrises and the latest sunsets.

Fall is the season after summer. During fall, the temperature gets cool and the number of daylight hours begins to decrease. The leaves on some trees begin to change color and fall away. This will help them to save energy during the approaching winter.

During winter, the Earth is tilted away from the Sun. The weather is the coldest and the days are the shortest. The Sun rises later in the morning and sets in the late afternoon. In some parts of the Earth, winter is also the season when it is most likely to snow. The ground may be covered in ice and lakes and streams may freeze. Some animals become inactive or migrate to warmer places during winter.

As winter moves to spring, the number of daylight hours increases and the temperature gets warmer. Spring is the season for reproduction. Trees regrow their leaves and start to produce flowers. Animals become active and also reproduce during spring.

summertio mer fall winter Activity 9.6AB Regal warm war to spring, the numb pring, the nu rs increases and the ncreases and gets warmer. Spring s warmer. Sp reproduction. Trees oduction. Tr es and start to prod start to pro s become active and come active an duce during spring. during sp Re Activ R A educ est Sun Su s in s of the the n when it n it round may nd may s and streams d stream ecome come aces aces

spring

67

A Closer Look Graphing Weather

Scientists are constantly collecting data about the weather. They often create tables and graphs to help them understand nd seasonal changes in weather. Tables and charts are also a useful so use way to communicate weather information to people. Let’s take a look at the yearly changes in weather for San Francisco, United States.

Average Daylight Hours – San Francisco Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 10 11 12 13 14 14.5 14.5 13.5 12.5 11.5 10 9.5 San uca uc c cau n Francis Aug S 5 14.5 14.5 13.5 1

Average Precipitation – San Francisco verag era cipitii

Jan 0 mm 20 mm 40 mm 60 mm 80 mm 100 mm 120 mm May Sep Mar Jul NovFeb Jun OctApr Aug DecRe Regega Jan 0 mm mm mm m Feb

68

How does the weather change throughout the year in San Francisco?atitio ow does the change thro year in Sa

25oC

20oC

15oC

10oC Average Maximum Temperature – San Francisco um Temp m Temp

a al

5oC

RJan 0oC May Sep Mar Jul NovFeb Jun OctApr Aug DecJa J n MarFeb Feb

AB Activities 9.7 – 9.8

69