The need for climatological data of the North Sea has increased during the past years. The increase in offshore and recreational activities can benefit greatly from such data. In order to meet this need weather observations made by ships and lightvessels in the North Sea have been processed extensively, which has resulted in a large number of tables, charts, etc. with climatological data. This publication gives a selection of these data, in which the emphasis lies on wind and wave data. In addition, some characteristic data on air and sea tempera ture, cloud cover, precipitation, visibility and sea level pressure are given. With regard to the observations of the lightvessels the publication can be consi dered as a continuation of earlier work. It also concludes the era of observations made by crew on board lightvessels, which gradually ended in the 1970's. The observations on fixed platforms which are now replacing the observations of the lightvessels are of a quite different character. The data are based on observations made on board lightvessels during the period 0 1949 -1980 and voluntary observing ships in the area between 51 ON and 60 N during the period 1961-1980. The observations of the lightvessels have been compared with those published for earlier periods (1859 -1883, 1884 -1909 and 1910 -1940). The manuscript (or part of it) has been critically examined by Prof.Dr.Ir. J.A. Battjes, E. Bouws, Dr.Ir. J.A. Buishand, H.A.M. Geurts, Dr. GJ.Komen, Dr. G.P.