Spring break
Moosonee has a humid continental climate (Köppen climate classification "Dfb"), with warm summers and cold winters. James Bay acts as a thermal reservoir to moderate spring and fall temperatures. Freeze-up on the Moose River normally occurs between late November and mid-December, with mean daily minimum January temperatures approximately . Spring break-up, or spring thaw, usually occurs in April. Mean annual precipitation is approximately , and mean annual snowfall is approximately . Precipitation is somewhat higher in summer than at other times of the year. Severe thunderstorms can occur from time to time. Moosonee used to have a subarctic climate with a yearly mean temperature of −1.3 °C (29.7 °F), but due to global warming that temperature has risen.