Having just heard for the first time that a true Indian summer has to be preceded by a freeze, I did a little googling and found this page, which contains detailed investigations of the phenomenon itself and of the possible origins of its name (which goes back at least to a letter by St. John de Crevecoeur dated "German-flats, 17 Janvier, 1778"). The consensus definition:
It is an abnormally warm and dry weather period, varying in length, that comes in the autumn time of the year, usually in October or November, and only after the first killing frost/freeze. There may be several occurrences of Indian Summer in a fall season or none at all.Posted by languagehat at November 6, 2003 09:37 AM
My father-in-law told me the same thing a few weeks ago. I figured the difference in our usages (he required the frost; I only needed a cold spell) were due to his being a New Englander and my being from Louisiana. Thanks for the further elucidation.
Posted by: T. Carter at November 6, 2003 10:09 AMGoogling some some, the Glossary of Meterology compares Indian Summer with Old Wives' summer, St. Martin's summer, St. Luke's summer and All-hallown summer.
Digging more, Altweigersommer appears to be the term in German, and été des Indiens in Québécois.
Flipping though a few random dictionaires, I found babie lato (Polish); Schmokdaage, Schmokwedder and Altweiwersummer (Pennsylvania German); бабье лето (Russian); brittsommar and indiansommar (Swedish).
I asked a Chilean colleague, and he saw veranillo de San Martín in a dictionary, but left a message with a friend because he couldn't remember the term they used back home. A Brazilian colleague insisted that it is summer year round in Brazil thus no need for such a term.
Posted by: T. Carter at November 6, 2003 11:37 AMHuh. Sue and I were just speculating about where the name came from two days ago. Thanks for the link!
Posted by: Chris at November 6, 2003 12:49 PM