From the data of meteorological observations for 20 years (1975-1994) in St. Petersburg and Belogorka, the recurrence of fogs and hazes for day and night in all seasons is determined. It is calculated for three types of fogs and hazes, namely, heavy, moderate, and light. Contrary to the expectations, the recurrence of fogs in a big city is much smaller (up to 2-3 times) than under rural conditions. This conclusion about fogs has already been drawn in our papers. However, the conclusion about lower recurrence of hazes in St. Petersburg, as compared to the rural conditions, is formulated for the first time. The seasonal and diurnal variations of the recurrence of fogs and hazes are considered. The recurrences in the daytime and at night are close to each other. This indicates the determining factor of advection in formation of fogs and hazes. The paper presents the data on duration and probability of formation of fogs and hazes and on difference in relative humidity in St. Petersburg and Belogorka when fog or haze are formed at the second point given that they are absent at the first point. The variation of the liquid water content of fog under the effect of temperature elevation is estimated.