Seasons in the Northern Hemisphere
September 23 officially welcomes Fall 2007. Say good bye to summer. 
It’s one of two times a year when the sun crosses the equator, and the day and night are of approximately equal length.
The sun is above the equator and night and day are of approximately equal length; the word equinox is often used to refer to either of these dates.
The Autumn equinox signals the beginning of Fall. It is the point where there is exactly 12 hours of daylight and 12 hours of darkness at the equator. If you live anywhere else, however, you will see a little bit more or a little bit less than 12 hours of daylight. The daylight hours are dwindling and will continue to do so until we reach the Winter Solstice, the shortest day of the year and the start of winter.
