The best time to go to Vermillion, South Dakota, is during the late spring to early fall, specifically from May to October, when the weather is most pleasant for outdoor activities and local events.For those planning to visit the University of South Dakota or enjoy outdoor recreation, May, September, and October offer comfortable temperatures. These months are ideal for exploring the Missouri River, walking around campus, or attending university-related events without the intense heat of summer.Families visiting during the summer months of June, July, and August will find plenty of daylight and warm weather suitable for activities like exploring the Spirit Mound Historic Prairie or fishing on the Missouri River.