Newfoundland and Labrador is home to a variety of climates and weather. One of the main reasons for this diversity is the geography of the province. The province spans 5.5 degrees of latitude, which is comparable to that of the Great Lakes. The province has been divided into six climate types, but in broader terms Newfoundland has a cool summer subtype of a humid continental climate, which is greatly influenced by the sea since no part of the island is more than 100 km (62 mi) from the ocean. Northern Labrador is classified as a polar tundra climate, southern Labrador have a subarctic climate.

Monthly average temperatures, rainfall and snowfall for four communities are shown in the attached graphs. St. John's represents the east coast, Gander the interior of the island, Corner Brook the west coast of the island and Wabush the interior of Labrador. The detailed information and information for 73 communities in the province is available from a government website. The data used in making the graphs is the average taken over thirty years. Error bars on the temperature graph indicate the range of daytime highs and night time lows. Snowfall is the total amount which fell during the month, not the amount accumulated on the ground. This distinction is particularly important for St. John's where a heavy snowfall can be followed by rain so that no snow remains on the ground.

Surface water temperatures on the Atlantic side reach a summer average of 12 °C (54 °F) inshore and 9 °C (48 °F) offshore to winter lows of −1 °C (30.2 °F) inshore and 2 °C (36 °F) offshore. Sea temperatures on the west coast are warmer than Atlantic side by 1 to 3 °C (1 to 5 °F). The sea keeps winter temperatures slightly higher and summer temperatures a little lower on the coast than at places inland. The maritime climate produces more variable weather, ample precipitation in a variety of forms, greater humidity, lower visibility, more clouds, less sunshine, and higher winds than a continental climate.