This week's unusually warm weather may have metro-east residents wondering when the weather will cool down.
Although December 21 isn't officially the start of winter, the St. Louis area could see lower autumnal temperatures before then.
Alex Elmore, a meteorologist with the National Weather Service in St. Louis, told the News-Democrat on Monday.
"We're going to get a true taste of fall this weekend, it's going to be quite cool."
In fact, this weekend's temperatures are expected to be below average, with Saturday lows in the 40s.
A number of cold fronts are to blame for the impending temperature decline, while other weather patterns last much longer than these regular drops.
El Niño is starting to develop for the first time in a number of years. El Niño and La Niña are names used to describe patterns of climate.
El Niño is seen when warm water is forced eastward by weakening tradewinds, according to data from the National Oceanic and Atmospheric Administration.