WINNIPEG, Manitoba—The hottest market for the ice-cold beverage known as the Slurpee isn't a tropical town in Florida or an Arizona desert spot.

It is Winnipeg, Manitoba, where the average daily temperature from December through March is only 10 degrees.

The Manitoba market, on the Canadian prairie, on Friday will be crowned the world's "Slurpee Capital" for the 15th year in a row—the only region to ever hold the honor even once.

7-Eleven Inc. since 1999 has tallied up Slurpee sales in each of its 87 markets in the U.S. and Canada. The one with the highest average sales of Slurpee units per store takes the title.

Manitobans' dynasty stems from their preternatural desire to slam Slurpees year-round.