Fog is a meteorological process quite frequent along, the Danube- Black Sea Canal, the average number of fog days being 45-48 days a year. In the lower layers of the atmosphere, entering in contact with the active underlying surface, after clear warm days during which intensive processes of evaporation occur, often the fog phenomenon arises, due to the droplets of water or ice crystals which are in suspension. The average number of fog days occurs differently from one season to another, the highest frequency being encountered during winter and autumn. Fog is most frequent at night, especially during the first hours after sunset and before sunrise. We may say that fog is a phenomenon which arises partly because of the water and because the region has an aisle character. During foggy days the river traffic on the Danube- Black Sea Canal is hindered or even stopped when the fog is very dense.
Key words: radiative – advection fog, thermal inversion, upwelling phenomenon.