UPDATE: The City of Sioux Falls announced that outdoor pools will close on Aug. 16, a week later than originally planned. SIOUX FALLS — Outdoor pools throughout Sioux Falls are preparing to close for the season after seeing an increase in traffic from last year. The City of Sioux Falls announced this week an Aug. 9 close date for outdoor pools throughout town. The first event will be held Aug. 11 at Terrace Park Family Aquatic Center, with a second opportunity Aug. 13 at Laurel Oak Family Aquatic Center. While outdoor pools will close to human swimmers Aug. 9, splash pads throughout Sioux Falls will remain open a little while longer.