FPUS43 KDMX 162107 City Forecast for Ottumwa, IA Issued Tuesday afternoon - Aug 16, 2011 .Tuesday night... Low 67, 40% chance of precipitation. .Wednesday... Partly cloudy, high 83, 20% chance of precipitation. .Wednesday night... Low 59, 5% chance of precipitation. .Thursday... Sunny, high 84. .Thursday night... Low 64.