Researchers say a tornado in southern Alberta, between Calgary and Red Deer, on Canada Day was the worst in that province since a deadly twister in 1987.

Environment Canada says 12 homes were hit by the tornado and several of those were destroyed.

Only one person suffered minor injuries.

Survey teams with the Northern Tornadoes Project, in conjunction with Environment Canada, found enough evidence to rate the tornado an EF4 (on the Enhanced Fujita scale which was implemented in 2013).

The teams said the tornado had a maximum wind speed of 275 km/h and it followed a preliminary path of more than 15 kilometres with a maximum width of 620 metres.

The Northern Tornadoes Project noted only 21 violent tornadoes across Canada have been rated at EF4 (F4) or higher.

Officials say weather alerts sent to mobile devices in advance of the tornado likely helped prevent fatalities.

This was the worst tornado in Alberta since a 1987 twister (rated F4 at that time) in Edmonton killed 27 people and destroyed hundreds of homes.