The Earth's seasons are the result of the tilt of the Earth's axis. The Earth's axis is tilted from perpendicular to the plane of the ecliptic by 23.45°. This tilting is what gives us the four seasons of the year - spring, summer, autumn and winter. Since the axis is tilted, different parts of the globe are oriented towards the Sun at different times of the year.
In each hemisphere summer is warmer than winter because the Sun's rays hit the Earth at a more direct angle during summer than during winter and also because the days are much longer than the nights during the summer. During the winter, the Sun's rays hit the Earth at an extreme angle, and the days are very short. These effects are due to the tilt of the Earth's axis.
The solstices are days when the Sun reaches its farthest northern and southern declinations. The winter solstice occurs on December 21 or 22 and marks the beginning of winter which is the shortest day of the year. The summer solstice occurs on June 21 and marks the beginning of summer which is the longest day of the year.
Equinoxes are days in which day and night are of equal duration. The two yearly equinoxes occur when the Sun crosses the celestial equator. The vernal equinox occurs in late March and is the beginning of spring in the Northern Hemisphere and the beginning of fall in the Southern Hemisphere. The autumnal equinox occurs in late September and is the beginning of fall in the Northern Hemisphere and the beginning of spring in the Southern Hemisphere).
The following pages have a different piece of clip art on each page.
Page 1 - The Four Seasons
Page 2 - Winter Tree
Page 3 - Spring Tree
Page 4 - Summer Tree
Page 5 - Autumn Tree