Environment Canada upgraded its tornado watch to a warning just after 6 p.m. Sunday for areas southwest of Edmonton and then downgraded the advisory back to a watch about 30 minutes later.

Clearwater County near Rocky Mountain House and Crimson Lake as well as areas of Ponoka County near Rimbey, Bluffton and Hoadley were put on critical alert for a possible tornado.

The agency had issued a tornado watch earlier Sunday afternoon for Drayton Valley, Devon, Rimbey and Pigeon Lake and for parts of Brazeau and Clearwater counties as Environment Canada meteorologists tracked a severe thunderstorm.

The advisories come as heat and thunderstorm warnings continue for most of central and south Alberta.

A tornado can produce strong wind gusts, hail the size of ping pong balls and heavy rain. Environment Canada has a list of tips if a tornado warning is issued for your area.

"Go indoors to a room on the lowest floor away from outside walls and windows, such as a basement, bathroom, stairwell or interior closet," Environment Canada says.

People are advised to leave mobile homes, vehicles, tents, and other free-standing shelters and take refuge in a building.

A landspout tornado was spotted east of Edmonton in early June. Funnel clouds can appear with little or no warning and should be treated serious, the agency warns.