SIOUX FALLS, S.D. (KELO)– If you were up early enough, you probably felt the chill in the air. Temperatures this morning fell to their coldest reading this month in Sioux Falls and surrounding areas, with many in the 40s. In the river valleys, it has been even colder, reaching into the upper 30s. This is the coldest reading for many this month. On this graphic, Custer and Pine Ridge both fell to temperatures in the middle 30s.