Colonsay experienced a record setting 167-day-long frost-free period in 1978, which was, to the dismay of a number of residents, still not a long enough growing season for yams or sweet potatoes. The ship U-Sea Colonsay is named after the local potash mine.
The main economy of the area is agriculture featuring grain crops such as wheat, canola, barley, oats, rye, as well as lentils and peas. Livestock raised in the vicinity are cattle, hogs, sheep, and buffalo. The potash mine of Colonsay was first named Potash Corporation of Saskatchewan, Colonsay, IMC Potash Colonsay and is now Mosaic Potash Colonsay. Potash is mined and sold to crop nutrient manufacturers for fertilizer, as well as for use as icemelter ingredient and water softener regenerant.