In this study the method of fuzzy interference systems are used to evaluate fog forecasting. Input variables used in this study included the situation of fog parameters dew point, dew point spread, rate of change of dew point spread wind speed and sky coverage. The membership functions are generally trapezoids, although simpler functions such as triangles and rectangles and even delta functions are often used. The degrees of membership of the system inputs are also examined. The strength of a rule has been derived from the corresponding degrees of membership of the system inputs. Only 16 rules of the entire set of 144 would have non-zero values, or strengths. The techniques indicate some preliminary results using real data. The final system output is then calculated as the weighted average of the centroid of each membership function with the area of the enclosed set used as the weighting factor. These centroids and weighting areas of the current values were calculated to find the forecasting of fog. The result of this study would hopefully help the planners and program managers to take necessary actions and to development air, marine, and road traffic etc.