An advection fog forecasting system and a method thereof are based on the recognition that wireless signal communication is subject to weather conditions. The system and the method involve collecting radio signals in a forecasting region that is likely to be shrouded in fog. Radio signals influenced by fog can show fog attenuation, and different levels of attenuation can be represented by different values of a radio signal strength indicator RSSI. With the variation curve of the radio signal strength indicator RSSI and weather variables, such as the humidity, the wind speed and the rainfall in the forecasting region, forecasting advection fog can be achieved.