Southern Wisconsin is under a flood watch from 1 a.m. Saturday through Saturday afternoon as widespread rain and thunderstorms move through the region. The heaviest rainfall is expected overnight Friday, particularly after midnight. Forecasts call for many areas to receive 2 to 4 inches of rain, with locally higher totals possible. The flood watch projects generally 1 to 3 inches across the region, while areas affected by repeated storm bands could see 3 to 6 inches or more. The greatest flooding concerns are in low-lying areas, urban locations with poor drainage, and along rivers, creeks and streams. Excessive runoff could lead to both river flooding and flash flooding. The watch includes Dane, Columbia, Green, Green Lake, Iowa, Lafayette, Marquette, Rock and Sauk counties in south-central Wisconsin. It also covers Fond du Lac and Sheboygan counties, as well as Dodge, Jefferson, Kenosha, Milwaukee, Ozaukee, Racine, Walworth, Washington and Waukesha counties in southeastern Wisconsin. Scattered showers and thunderstorms are expected Friday evening, with breezy conditions developing before widespread heavy rain arrives overnight. The heaviest rain should move out by midmorning Saturday, but additional showers are expected through the day. Temperatures Saturday are forecast to remain mostly in the 60s, with some areas near Illinois briefly reaching the lower 70s. Showers could continue into Sunday morning, and another round of thunderstorms is possible Saturday afternoon or early evening in areas near Illinois if temperatures become warm and humid enough. A strong storm cannot be ruled out. Residents in flood-prone areas should monitor updated forecasts and be prepared to act if flood or flash-flood warnings are issued. Never drive through flooded roadways; even shallow, moving water can conceal dangerous conditions and wash vehicles off the road. The weekend will remain breezy, with cooler weather arriving next week. High temperatures Monday and Tuesday are expected to be in the lower 60s.