Autumnal Equinox
9:29pm CDT Monday, September 22, 2014

Many will see calendars reference the first day of fall this year to be, Tuesday, September 23, however this year is not an easy year to determine the first day of fall. The Autumnal Equinox actually occurs on Monday, September 22 for Western and North Central Nebraska. The official time of the Equinox (the moment when the Sun is positioned directly over the Earth's equator) is 9:29 pm CDT or 8:29 pm MDT Monday evening. The reason many reference Tuesday is due to the Universal Time of the Equinox. This year the official time occurs at 0229 UTC September 23. This is why you may see the two days referenced as the first day of fall.

Typically the day of the Universal Time occurs is the day most often references as the first day of fall. During daylight time there is a 5 hour difference between the start of the day for Universal Time to Central Daylight Time (6 hours for MDT). Thus whenever the Equinox occurs early in the day Universal Time, confusion may occur.

During the day of an Equinox, nearly every point on the Earth's surface has the same sunrise and sunset, (exception is when there is an obstruction to the horizon like a mountain). The autumnal equinox will occur on either the 22nd or 23rd of September. Below are the records for North Platte and Valentine for the both days, which show a wide range of weather is possible.

North Platte Records
Record September 22 September 23
High 93/1938 95/1921
Low 24/1995 23/1989
Lowest Max 48/1895 46/2000
Highest Min 63/1937,1891 67/2007
Precip 1.21/1941 .95/1941
Snow T/1895 0.3/2000

Valentine Records
Record September 22 September 23
High 95/1922 96/1905
Low 23/1989 23/1989
Lowest Max 46/1895 44/2000,1951
Highest Min 60/1929,1920 63/1958
Precip 0.97/1960 0.66/1941
Snow None T/1985

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