The seasons are a result of Earth's axis of rotation being tilted 23.5 degrees in respect to the plane of Earth's orbit around the sun. During one part of the year the Northern Hemisphere is faced toward the sun and the Southern Hemisphere is faced away from the sun. This produces summer in the Northen Hemisphere and winter in the Southern Hemisphere. Six months later,the situation is reversed. During March and September roughly about the time spring and fall begin in the Northen Hemisphere,both Hemisperes are receiving equal amounts of light.