Average climate in Milbank, South Dakota. Based on data reported by over 4,000 weather stations. Tornado activity: Milbank-area historical tornado activity is slightly below South Dakota state average. It is 7% smaller than the overall U.S. average. On 5/17/1996, a category F3 (max. wind speeds 158-206 mph) tornado 3.7 miles away from the Milbank city center caused $2 million in damages.