“Indian summer” is a phrase most North Americans use to describe an unseasonably warm and sunny patch of weather during autumn.
Weather Historian William R Deedler, of the National Weather Service, describes it as “any spell of warm, quiet, hazy weather that may occur in October or even early November”.
An Indian summer is typically caused by a sharp shift in the jet stream from the south to the north. The warm weather may last anywhere from a few days to over a week and may happen multiple times before winter arrives for good.
To be a true Second Summer, the following generally agreed upon criteria must be met:
- Temperatures must be above 70 degrees Fahrenheit for a period of at least seven days or more after the fall equinox.
- The heatwave must occur after the first frost.
No one really knows how the term “Indian summer” came to describe such periods. One theory suggests that early American settlers mistook the sight of sun rays through the hazy autumn air for Native American campfires, resulting in the name “Indian summer.” Others speculate that Native Americans recognized this weather pattern and used the opportunity to gather additional food for the winter.
Who Experiences Indian Summers?
Indian summer is a common occurrence not only in North America but also throughout temperate European countries, where it is most commonly called “St. Martin’s Summer.” The name is a reference to St. Martin’s Day, which falls on November 11. Many countries, including England, Italy, Portugal, and Sweden, have traditional outdoor festivals in the week leading up to St. Martin’s Day.
Other popular variations include “Second Summer,” “St. Luke’s Summer,” in reference to St. Luke’s Day on October 18, “All-Hallown Summer,” in reference to All Saints Day on November 1, and the more popularly celebrated “All Hallow’s Eve,” or Halloween.
If you find yourself in the midst of a “second summer,” take advantage of it! Finish that last little bit of yard work, take the boat out one more time, or have a picnic in the park. Soak in the sunshine because winter will not be far behind.