听力原文： Indian summer is a short period of extremaly fair weather and mild days in autumn. It comes in late October or early November while the leaves are turning color and falling from the trees. It has no definite day of beginning or ending. The pleasant weather follows the autumn's first period of cold, wintry days. The days become warmer but the nights remain chilly. An Indian summer moon often has a soft yellow or orange hue. Indian summer lasts from a week to ten days and sometimes for two weeks. Then winter starts. Indian summer is caused by a large mass of warm tropical air. South winds carry these masses northward. The American Indians enjoyed Indian summer and called it a gift of a favorite god- the god of the Southwest. At what time of the year does Indian summer come?