We in the Norhteast are currently having wonderful weather-clear days, with highs around 75 F. Is this “Indian Summer”? I thought that Indian summer is the time from when the leaves drop (usually mid-October), until the first hard frost. Is there any meteorological explanation for why there should be an apparent warming in late October? or is the just another myth.
Still, i like the name “Indian Sunner”-wasn’t there a POCO song of the same name?
The current heat is simply part of Summer. We tend to think of September as Fall because by Labor Day we’ve gotten the kids boxed up in those neat holding facilities again and everything after “back to school” gets shoved in with Fall. However, as you noted, actual Indian Summer doesn’t occur until the weather has turned cool and we get one last shot of warmth. Cecil mentions the origins of the phrase, in passing, in What’s the origin of the expression “Indian giver”?
I have no idea what meteorological phenomenon causes it. It may be nothing more than a perception: as the weather cools through the season, the temperatures do not fall on a straight line from the 80s to the 20s (F) and if there is a period where they bounce from the 50s or 40s back to the 70s for a few days, we pounce on that as Indian summer, whereas during the summer, we do not assign a name to periods of 80° weather followed by 60° weather followed by 90° weather.
We have a similar experience in the Great Lakes region (I don’t know how widespread it is) where we will get sub-zero temperatures around the beginning of January and a warming trend into the 50s (and rarely into the 70s) near the end of January that is sometimes called “our January thaw”. I have never looked to see whether that is a genuine weather phenomenon or simply a perception.
The flow of the jet stream changes with the seasons. In the fall and winter it develops large north/south loops, which can bring back days of summer-like warmth.
This NOAA site quotes a reference to Indian Summer that dates back to 1778.
I have heard that Indian Summer refers to a period of abnormally warm weather following the first killing frost or freeze.
It is possible to have more than one in the autumn.
Random House says the meaning of “Indian” in the phrase is uncertain:
The story I had always heard was that it was similar to “Indian corn:” i.e. not “false” corn, but rather “corn of the Indian country.”
There are weather reporters who will tell you that Indian Summer is a period of warming (I don’t believe an exact temperature has been cited, but give them time) following the first frost of the season. Unfortunately, these are also the same people who try to tell you that Autumn begins on the Equinox, in direct contradiction of Cecil:
http://www.straightdope.com/classics/a1_170b.html
Basically, Indian Summer is any bright, clear, warmer-than-usual day coming after you think the weather has turned crappy for the season.
As for why? Average temperatures are just that: averages. Weather fluctuates. Warm spells follow cold spells, for a million and one reasons. A decent warm spell following a noticeable cold spell after the end of hot, humid Summer? That’s Indian Summer. Enjoy it.
– Beruang