FPUS42 KJAX 211310 City Forecast for St Augustine, FL Issued Tuesday morning - May 21, 2013 .Tuesday... Partly cloudy, high 82, 30% chance of precipitation. .Tuesday night... Low 69, 20% chance of precipitation. .Wednesday... Partly cloudy, high 82, 30% chance of precipitation. .Wednesday night... Low 68. .Thursday... High 85.