This is the most common explanation found in almanacs. It posits that early European settlers noticed Native Americans using the warm spell to harvest their final crops and increase their winter stores.
Daytime temperatures must be significantly higher than the average for that time of year, often reaching into the 70s or 80s (Fahrenheit), while nights remain cool. Where Did the Name Come From? indian summer definition
Temperatures must be significantly above average for the time of year, often reaching into the 70s or 80s Fahrenheit (20s Celsius). This is the most common explanation found in almanacs