Out of the fours seasons of the year, Fall is definitely my favorite time of year. I love everything about it especially the way the leaves change to the most beautiful colors you can imagine. This post will address changes in our environment and why seasons change. The information contained below was taken from an internet search for answers to the following questions:
WHY DO SEASONS CHANGE?
Seasons change because the axis of the earth is tilted by 23.5 degrees (from a line perpendicular to its orbit). As the earth moves around its orbit there is a time when it is tilted towards the sun and so receives a higher concentration of the sun’s energy (summer) and a time when it is tilted away and receiving less energy (winter). This also explains why it is summer in N hemisphere when it is winter in S hemisphere.*
HOW IS THE CHANGING OF THE SEASONS DETERMINED?
Summer starts with the Summer Solstice. The solstice is defined as the longest daylight of the year, with the shortest 
night. The solstice always comes in late June in the northern hemisphere. (If you are in the southern hemisphere you will have your Winter Solstice and the start of Winter when we have our first day of Summer)
After Summer, Autumn (or Fall) begins on the Autumnal Equinox. The equinox is defined as the day when day and night are of equal length on all parts of the globe, approximately 12 hours each. Fall officially begins in late September.
The first day of Winter aligns with the Winter Solstice, the opposite of the Summer Solstice and the shortest day of the year with the longest night. This occurs in late December in the northern hemisphere.
Spring begins on the Vernal Equinox, again when day and night are approximately equal all over the globe. This usually falls in late March.*
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