An Indian summer is a heat wave tthat happens in the Autumn when there is a spell of above-normal temperatures, often with dry and hazy conditions, usually after there has been a hard frost.
For the Northern Hemisphere it usually occurs between late September and mid November. It is a spell of unseasonably warm, dry weather after the end of Summer.
It was originally an American phrase and in English the phrase St Martin’s Summer was used, refering to 11th November which is St Martins’ Day.
We are hoping, as you probably are, for a long Indian Summer this year so we can continue with warm evenings for our hot air balloon flights!