On October 24 and 25, 1997, a blizzard dumped nearly two feet of snow on Denver and up to four feet on neighboring communities, stranding thousands. Four people and thousands of livestock died. “People were not prepared to go from a gentle, mild fall to a true blizzard in a matter of a few hours,” says Nolan Doesken, a state climatologist with the Colorado Climate Center, who spent that night trapped in a car on I-25. Part of the blame for the storm lay with El Niño, a current of unusually warm water in the tropical Pacific Ocean that mixes with weak easterly winds to alter the world’s jet streams. That results in colder, wetter winters in the southern part of the United States and the opposite in the northern states. Colorado—and Denver in particular—sits between the two. Usually. The capricious weather system comes around every two to seven years, often without incident in Colorado; occasionally, however, we catch the uppermost tip of the southern weather pattern, which results in abnormally large snowstorms. In fact, since 1950 four of the five largest snowstorms in Denver have occurred during El Niño years. The weather system is expected to be back again in 2015 and is “significant and strengthening,” according to NOAA at press time. Which could be superb news for powder hounds, whose best chance for a killer snow day, says Joel Gratz, a meteorologist at weather blog OpenSnow, is to make like geese and head south to spots such as Wolf Creek Ski Area, Telluride Ski Resort, Silverton Mountain, and Purgatory Resort.