<P> The United States has the most tornadoes of any country . Many of these form in an area of the central ( with some definitions including Southern ) United States known as Tornado Alley . This area extends into Canada , particularly the Prairie Provinces and Ontario ; however , activity in Canada is less frequent and intense than that of the US . The high frequency of tornadoes in North America is largely due to geography , as moisture from the Gulf of Mexico is easily advected into the midcontinent with few topographic barriers in the way . The Rocky Mountains block Pacific - sourced moisture and buckle the atmospheric flow , forcing drier air at mid-levels of the troposphere due to downsloping winds and causing cyclogenesis downstream to the east of the mountains . Downsloping winds off the Rockies force the formation of a dry line when the flow aloft is strong , while the Gulf of Mexico fuels abundant low - level moisture . This unique topography allows for frequent collisions of warm and cold air , the conditions that breed strong , long - lived storms throughout the year . This area extends into Canada , particularly Ontario and the Prairie Provinces , and strong tornadoes can also occur in northern Mexico . </P>
<P> The United States has the most tornadoes of any country . Many of these form in an area of the central ( with some definitions including Southern ) United States known as Tornado Alley . This area extends into Canada , particularly the Prairie Provinces and Ontario ; however , activity in Canada is less frequent and intense than that of the US . The high frequency of tornadoes in North America is largely due to geography , as moisture from the Gulf of Mexico is easily advected into the midcontinent with few topographic barriers in the way . The Rocky Mountains block Pacific - sourced moisture and buckle the atmospheric flow , forcing drier air at mid-levels of the troposphere due to downsloping winds and causing cyclogenesis downstream to the east of the mountains . Downsloping winds off the Rockies force the formation of a dry line when the flow aloft is strong , while the Gulf of Mexico fuels abundant low - level moisture . This unique topography allows for frequent collisions of warm and cold air , the conditions that breed strong , long - lived storms throughout the year . This area extends into Canada , particularly Ontario and the Prairie Provinces , and strong tornadoes can also occur in northern Mexico . </P>
which continent experiences the highest number of tornadoes per year
which continent experiences the highest number of tornadoes per year
North America
North America