seasons of the year![click to hear](/images/speaker.jpg)
Periodic climate changes over the course of a year; they are a function of the Earth’s inclination toward the Sun and its rotation around it.
Sun ![click to hear](/images/speaker.jpg)
Source of the Earth’s heat.
autumnal equinox ![click to hear](/images/speaker.jpg)
At the equinoxes, day and night are of equal length; the autumnal (fall) equinox is on September 22 or 23 in the Northern Hemisphere.
autumn ![click to hear](/images/speaker.jpg)
Season between the autumnal equinox and the winter solstice.
winter solstice ![click to hear](/images/speaker.jpg)
Shortest day of the year; it falls on December 21 or 22 in the Northern Hemisphere.
winter ![click to hear](/images/speaker.jpg)
Season between the winter solstice and the vernal equinox.
summer ![click to hear](/images/speaker.jpg)
Season between the summer solstice and the autumnal equinox.
summer solstice ![click to hear](/images/speaker.jpg)
Longest day of the year; it falls on June 21 or 22 in the Northern Hemisphere.
spring ![click to hear](/images/speaker.jpg)
Season between the vernal equinox and the summer solstice.
vernal equinox ![click to hear](/images/speaker.jpg)
At the equinoxes, day and night are of equal length; the vernal (spring) equinox is on March 20 or 21 in the Northern Hemisphere.