Falling through fall. Why the beginning of the new season means big changes in temperature.

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BRIDGEPORT, W. Va. (WDTV) - The beginning of fall means that the direct rays of the sun are over the equator. This is the halfway point of it's journey to the Tropic of Capricorn which is at 23.5 degrees south latitude. The beginning of summer had the sun directly over the Tropic of Cancer at 23.5 degrees north latitude. The direct rays of the sun (straight up at noon) moves (or 'turns') between these two extremes during the year.

The word 'tropic' has the root word 'trop', which means to 'turn'. Hence where we get the term from. The sun 'turns' between these two latitudes through the year. The higher sun in the sky keeps days longer and warmer there.

Back to West Virginia. As fall begins, the sun gets lower in the sky as it travels south of the equator. This means that days are shorter through fall and the shortest as winter begins. Shorter days means longer nights.

As daylight hours wane and nighttime lengthens, we get less heat, and more time to get rid of it. If we think of sun as heat, and heat as temperature, and temperature as money, we use a bank account analogy to show why it gets colder during fall.

If we take out more money than we put in the bank, our account gets lower and lower. Short days is little money and long nights are big withdrawals. This means we will get colder as we go through fall.

Temperatures on average drop faster in early to middle fall. The rate of temperatures falling, on average, is slower in the late fall and as we close in on winter. This is because the difference in change of daylight to nighttime is greatest earlier in the fall season.