The name Indian Summer refers to a quiet and hazy period in autumn that occurs after the first killing frost/freeze. Temperatures are above normal and this mild, tranquil pattern can last for a few days up to a week.
Looking at a weather map of this scenario, you would see an area of high pressure off the east coast and experience winds out of the south/southwest. These winds bring up the milder temperatures from the south.
The mild spell ends once a strong area of low pressure with a cold front sweeps through the region. The winds shift then to a colder northwesterly flow.
John Bradbury wrote a great description of Indian Summer back in 1817, "The air is perfectly quiescent and all is stillness, as if Nature, after her exertions during the Summer, were now at rest."
It is not completely known where the term Indian Summer comes from. One theory suggests that this was the time of year that the early native Indians hunted.
The animals would come out during the mild and hazy weather. The hazy conditions then allowed hunters the ability to sneak up on their prey more easily.
Indian Summer usually occurs near the end of October or early November. Though it is only here for a short while, you can have more than one Indian Summer during the fall.
