The weather changes quickly on the Canadian prairies. The old saying of "if you don't like the weather, wait 10 minutes" definitely applies here.
In the summer, thunderstorms can form rapidly and move quickly. They are associated with short periods of intense rain, thunder and lightening, wind, hail and sometimes even a tornado.
I was driving south of Calgary on a nice sunny day when I saw this storm approaching from the west. I thought the sun shining on a canola field in bloom in the foreground contrasted nicely with the gloom coming in from the Rocky Mountains.