Because in America, September is the month of fall or autumn. Technically, the season of fall or autumn signals that summer season has ended. But why is there a word "unofficial", you may ask. It is because it is not mandated by state law!
State law must not require it to be official end of summer. There's no such legislation regarding the end or beginning of a season. That will be weird. It's a season, not a holiday!
Here are the astronomical months of the start of each season in US:
- Spring - March to May
- Summer - June to August
- Fall: September to November
- Winter: December to February
Find out what season it is in Australia when North America is experiencing summer: https://brainly.com/question/854681
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