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Climate

Northern Hudson Bay has a polar climate (Köppen: ET) being one of the few places in the world where this type of climate is found south of 60 °N, going farther south towards Quebec, where Inukjuak is still dominated by the tundra. From Arviat, Nunavut, to the west to the south and southeast prevails the subarctic climate (Köppen: Dfc). This is because in the central summer months, heat waves can advance from the hot land and make the weather milder, with the result that the average temperature surpasses 10 °C (50 °F). The bay receives water from various surrounding rivers and currents originating from the Foxe Basin in the north, resulting in a counterclockwise overall flow. At the extreme southern tip of the extension known as James Bay arises a humid continental climate with a longer and generally hotter summer. (Köppen: Dfb). The average annual temperature in almost the entire bay is around 0 °C (32 °F) or below. In the extreme northeast, winter temperatures average as low as −29 °C (−20 °F).

The Hudson Bay region has very low year-round average temperatures. The average annual temperature for Churchill at 59°N is −6 °C (21 °F) and Inukjuak, facing cool westerlies in summer at 58°N, an even colder −7 °C (19 °F). By comparison, Magadan, in a comparable position at 59°N on the Eurasian landmass in the Russian Far East and with a similar subarctic climate, has an annual average of −2.7 °C (27.1 °F). Vis-à-vis geographically closer Europe, contrasts stand much more extreme. Arkhangelsk at 64°N in northwestern Russia has an average of 2 °C (36 °F), while the mild continental coastline of Stockholm at 59°N on the shore of an analogous large hyposaline marine inlet – the Baltic Sea – has an annual average of 8 °C (46 °F).

Water temperature peaks at 8–9 °C (46–48 °F) on the western side of the bay in late summer. It is largely frozen over from mid-December to mid-June, when it usually clears from its eastern end westwards and southwards. A steady increase in regional temperatures over the last 100 years has led to decreases in the extent of the sea ice in Hudson Bay by 19.5% per decade. As well as a lengthening of the ice-free period, which was as short as four months in the late 17th century.

The polar climate of Hudson Bay means it is home for a variety of polar climate animals, in the Western Hudson Bay (WHB) beluga whale population is the most significant known group in the Canadian Arctic, estimated to consist of approximately 54,473 individuals.