Environment Canada reported a tornado touching down in a rural area eight kilometres north of Taber, and funnel clouds were spotted in neighbouring communities such as Brooks and Bow Island.
There were reports of some damage to farm buildings and trees being uprooted by high winds, and power was knocked out to about 3,000 customers in the Taber area.
RCMP said heavy winds and rains were resulting in zero visibility on the Trans-Canada Highway between Calgary and Bassano.
In Calgary and other southern communities, heavy rain produced flash flooding in intersections and low-lying areas and some regions were hit by hail and heavy lightning.
Although there were no reports of injuries, Taber police said concerned residents overwhelmed their phone lines, prompting them to issue a request that people not call unless there was an emergency, and then to use only 911.
The whole mess was triggered by a strong storm cell moving north out of Montana, prompting tornado warnings and watches between Coaldale and Taber.
Lethbridge was under a severe thunderstorm watch for all of the afternoon, and severe thunderstorm watches and warnings were still in effect late Tuesday night and early Wednesday.
(CJOC, The Canadian Press)