The Sanctuary location is characterized by a monsoon climate. According to many years of observation the beginning of winter (stable transition of 0oC) was on November 18. Northwesterly winds prevail in winter and southeasterly winds in summer. Winter is distinguished by long duration (4.5 months), relatively low temperatures for these latitudes, dryness of air and large number of clear days. The average monthly temperature of January, the coldest month of the year, is Ц11.3oC for Bolshoi Pelis Island, and Ц10.3oC and Ц11.7oC for  continental observation points, Gamov and Possiet, respectively. Northerly winds normally prevail on islands in winter, and westerly and northwesterly winds in continental observation points. In spring, southerly and southeasterly winds that bring cold and moisture prevail. The amount of precipitation (on Bolshoi Pelis Island rises from 16 mm a month in January to 30-75 mm a month in April-June), and the mean monthly temperature on Bolshoi Pelis Island from 3.8oC in April to 12oC in June.
Climate and HydrologySummer begins from July 1 (when the mean temperature passes the 15oC mark) and is accompanied by high precipitation and frequent fogs. The highest mean monthly air temperature in August is equal to 19.9oC on Bolshoi Pelis Island, and to 20.9oC in Possiet. The winds are preferentially southeasterly. In the area of Bolshoi Pelis Island, 80 percent of all days are overcast in July, 70 percent in August and 48 percent in September; the amount of precipitation drops from 115 mm in July and September to 114 mm in August; again, the number of foggy days in July equals 20%, in August 12% and in September 2%; humidity in July is 94%, in August 90% and in September 80%.
    Fall is warm and dry with sunny days prevailing; starts on September 11. Mean air temperature in October is 9.8oC, and in November 0.6oC; from 52 to 53% of all days are fine, precipitation in October is 40 mm, and in November 34 mm; the first light frosts are noted from the second half of October.
 Thus,the climate in the Sanctuary area is characterized by well-pronounced degree of contrast.
    The hydrological conditions in the Sanctuary waters are likewise rather contrasting. In  January, the mean sea surface temperature drops to Ц1.8oC to reach 20.5o and 23.2oC in August in Bolshoi Pelis Island and Possiet Bay, respectively. In summer, the vertical temperature distribution in the upper sea layers in half-closed inlets is characterized by considerable gradient decrease with depth. For instance, in Possiet Bay, at temperatures ranging from 22 to 23oC, at 20 m deep the water temperature is from 12 to 13oC. At the same time, the difference between the surface water temperature and that of waters of up to 30 m deep does not exceed 2-3oC, this being ostensibly due to mixing. In the open sea, the temperature in summer at 50 m deep equals 3.4oC, and at 100 m deep 1.23oC.
    Thus, in winter the Sanctuary waters are similar in temperature with that in the Arctic and in summer with subtropical temperatures. And yet, at relatively small depths the temperature is significantly lower than that in surface waters, this being a prerequisite for simultaneous existence of warm-water and cold-water species in the same inlets.
    Water salinity off Bolshoi Pelis Island varies from 34.0o/oo (January) to 32.5o/oo (August). In Possiet Bay, it drops in summer to 27.3o/oo, while in the river-freshened Sivuchya Inlet there are sectors with strongly decreased salinity, where marine species are correspondingly replaced by salt-water species.
    The Sanctuary waters are characterized by relatively high transparency compared with that in other parts of the Bay, maximum transparency being observed at Stenin Island. The coastline water color is greenish-yellow, and that off Stenin Island greenish-blue. Despite the proximity of Vladivostok, a large city and seaport, and the pollution of Amur Bay, the waters around Rimsky Korsakov Islands are amazingly clear. Quite probably, this is caused by water circulation around Rimsky Korsakov Archipelago, forcing out polluted waters to other areas.
    High tides in the Sanctuary are irregular, occurring twice a day and not exceeding 0.5 m in amplitude. A combination of various types of currents in surrounding bays and at nearby islands results in a highly complex hydrological situation to cause strong and stable currents with movement of surface and deeper waters, rotations and, finally, among other things and in some half-closed inlets, such weak water movement as to cause waters with considerably different temperatures at the surface and sea floor to stratify in summer.
    In addition to the cold Primorye Current flowing from north to south, hydrologists recorded circular currents, for instance around the islands of Rimsky Korsakov and Askold, as well as another current passing  along the coast from the south of Korea to the northeast. The coastal current perpetually brings from the south species novel to Primorye, which adapt successfully here.

A. TIURIN, Cand. Sci (Biology).