What is the autumn (fall) period?
August through November, all inclusive?
What about Winter, Spring and Summer?
Thank you.
In which country? Different parts of the world have different seasons, and even those with the four autumn/winter/spring/summer can have them at different times of the year?

In any case, it is hard to put a precise date on most of them.

In the UK, although the changes happen at approximately the same time each year, people judge it by the weather so it can vary by a month or so. I'd say roughly

Autumn - Very end of September to end November

Winter - December - March/April

Spring - April/May to end June

Summer - End June to end September.
In most of Australia (the southern hemosphere) we have;
Summer - December January February
Autumn - March April May
Winter - June July August
Spring - September October November.

In the North of Australia (near the Equator) we only have two seasons, Wet and Dry.
The wet season is at it's peak when it is summer in the south and the dry season is during the winter.
So people who can, migrate north for the winter (We call it the grey migration because it is mostly retired people).