St. John's has a humid continental climate (Köppen Dfb), with lower seasonal variation than normal for the latitude, which is due to Gulf Stream moderation. However, despite this maritime moderation, average January high temperatures are actually slightly colder in St. John's than it is in Kelowna, British Columbia, which is an inland city that is near the more marine air of the Pacific, demonstrating the cold nature of Eastern Canada. Mean temperatures range from −4.9 °C (23.2 °F) in February to 16.1 °C (61.0 °F) in August, showing somewhat of a seasonal lag in the climate. The city is also one of the areas of the country most prone to tropical cyclone activity, as it is bordered by the Atlantic Ocean to the east, where tropical storms (and sometimes hurricanes) travel from the United States. The city is one of the rainiest in Canada outside of coastal British Columbia. This is partly due to its propensity for tropical storm activity as well as moist, Atlantic air frequently blowing ashore and creating precipitation.

How is the climate in St. John's?