The United States are entirely located in the Northern Hemisphere. It is bordering Canada on the north, and the air masses that form over it have big influence on the climate of the United States. Most of the United States falls under the influence of the air masses coming from the north, with only the southern parts of the east and west coastlines not being heavily affected. The air masses that form over Canada are cold continental air masses. They move towards south, thus toward the United States in November, quickly pushing the warmer air masses, and replacing them, bringing in cold weather conditions, which last until March.