Astronomical Fall begins today at 10:29 PM EDT. The Autumnal Equinox occurs when the geometric center of the Sun's disc crosses the same horizontal plane as the Earth's equator on its way south as the Earth orbits the sun. The amount of daylight and dark are approximately 12 hours each. For more information on why the amounts of day and night are not exactly 12 hours, please visit the US Naval Observatory's website.
The average high temperature at Indianapolis for the Autumnal Equinox is 75 degrees. By the time Fall ends in December, the normal high temperature is 37. The warmest temperature ever recorded on the Autumnal Equinox is 93 degrees, in 1895. The coldest temperature recorded on the Autumnal Equinox is 34 degrees, last reached in 1995. The most rainfall is 2.11 inches, in 1955. Below is a chart with some additional information on temperatures on the equinox.