The weather is very balmy in much of the UK at the moment, but we haven't got an Indian summer, according to BBC weatherman Liam Dutton and Antony Woodward, author of The Wrong Kind of Snow, who were speaking on the radio this morning (listen for another week here). Indian summers are, technically, spells of warm weather in October or November that occur after cold and frosty weather. An old word for Indian summer is St Luke's Summer, and St Luke's Day is 18 October (I wrote a blog post on this last October 18, and mention Indian summers and old women's summers here). Antony Woodward said that the unexpected hot weather we are experiencing at the moment is just a warm spell, not an Indian summer.
The term Indian summer has nothing to do with the Indian subcontinent. The OED says it was originally (late 18th century) a North American expression, so presumably it refers to American Indians.
Listen to the piece for another week here.