The use of methods of complex climatology, which treats climate as a many-year weather re-gime, made it possible to define the annual structure of weather states observed in seven Polish sea ports, i.e. Elbląg, Gdańsk, Hel, Łeba, Ustka, Kołobrzeg and Świnoujście. This work uses data originating from OGIMET and covers the period 2000-2009. Weather conditions that make port operation either difficult or even impossible are considered to be those when, during a day, we observe negative air temperatures, cloudiness, precipitation and strong winds at the same time. Once the frequency of occurrence of unfavorable weather conditions has been defined for the port operation then for each port a climatogram was drawn illustrating their frequency in the following decades of a given year. Weather conditions which are unfavorable for the work in Polish sea ports are observed only in autumn and winter, and during early spring; they are most frequent in the ports of Ustka and Gdańsk. Their annual fre-quency in none of the described ports exceeds 1% so the conditions in Polish sea ports may be regarded as fa-vorable for port operations. The worst weather conditions are observed in the last decade of December, third decade in January and in the second and third decades in February as well as i the first decade of April.