Southampton Island has a severe
subarctic climate (
Köppen Dfc) which transitions into a
tundra climate (
ET). Like almost all of Nunavut, Southampton Island is entirely above the
tree line.
Coral Harbour has never gone above freezing in January, February and March (although the latter has recorded . Due to the frozen nature of
Hudson Bay, there is a severe
seasonal lag until June, especially compared to more continental areas such as
Fairbanks despite much sunshine and perpetual twilight at night. Due to the drop of solar strength and the absence of warm water even in summer, temperatures still drop off very fast as September approaches. Cold extremes are severe, but in line with many areas even farther south in Canada's interior. ==Flora==