The term Indian Summer has many proposed origins but the earliest to date gives credit to a letter written by Frenchman St. John de Crevecoeur in 1778. He described an Indian Summer as having a “tranquil atmosphere and general smokiness” following a period of cold before the true winter sets in. The term now most commonly and more formally describes a stint of warm weather in the fall, usually occurring just a few days after a frost. As it turns out this can usually be explained within the common fall meteorological patterns.
What we think of as Indian Summers generally occur when a high-pressure system moves through the area in mid-fall. The system first creates high, sparse cloud cover that serves as a poor insulator for the region and produces the frost and cool nights that typically precede this later than expected warmth. Often, the same high-pressure will draw warmer air from the southern regions and give us all one last chance for those shorts and sandals. The warm breezes from the south that are now waning ordinarily last from a few days to over a week.
The heat of an Indian summer is a wonderful time for getting out into the Arb to enjoy the fall colors and the changing of the season. The heat is not only attractive to humans but also to wildlife, so go ahead and take advantage of the lingering and quickly retreating hazy weather and walk about the Arboretum trails before you have to don your hat and gloves!
By Griffin Williams '12, for the Cole Student Naturalists