Indianapolis experiences sub-tropical humid climate. The weather in Indianapolis remains hot and humid during summer (June to early August). But the temperature during this period remains pleasant to move around the city.
Winters: Indianapolis' winters are often bitterly cold, with some exceptions: there are some relatively mild winters, winters are cold and continue from November to February.
Summers: Summer is, however, a good season to travel to Indianapolis. If you want to witness the city animation at its peak, then this is the best time to visit Indianapolis.
However, May receives maximum amount of rainfall. Like summer, autumn experiences similar mild temperature and it continues from end of August to October.
Spring is a transitional season, with very changeable weather: the transition from cold to hot weather often produces thunderstorms and tornadoes so this is considered as off season in Indianapolis.
Considering these facts, summer and autumn can be considered as the best time to visit Indianapolis.