FPUS43 KLSX 190820 City Forecast for St Louis, MO Issued Wednesday morning - Oct 19, 2005 .Wednesday... Partly cloudy, high 80, 30% chance of precipitation. .Wednesday night... Low 55, 50% chance of precipitation. .Thursday... Showers, high 70, 60% chance of precipitation. .Thursday night... Low 52. .Friday... High 63.