Observations of net radiation at Poste-de-la-Baleine (Great Whale) have shown that low cloud and fog are two important elements in the expianation of the climate along the South-East coast of Hudson Bay. Based on the hourly surface meteorclogical data for 1969, annual and seasonal frequencies have been established of the occurrence of low cloud and fog and their characteristics. From these frequencies, in association with other factors, it is possible to gauge to a certain extent the effect of low cloud and fog on the climate of Poste-de-la-Baleine (Great Whale). The results indicate that low cloud and fog were present at more than 50% of the observations in 1969, mainly during the period of daylight. Their high frequency, specially during the mild season, constitutes a dominant factor in the reduction of the energy available at the surface. Several consequences of their particular climatic conditions on human activities and on the vegetation are indicated.