(The Center Square) – For a third year in a row, it appears the country will see a La Nina weather pattern, but its effect on Illinois’ winter remains to be seen.
This is the first time in the 21st century that the meteorological system over the Pacific Ocean has returned for three consecutive years. The system occurs when strong winds blow warm water on the surface of the Pacific Ocean, resulting in cooler water rising to the surface.
According to the World Meteorological Organization, “the worsening drought in the Horn of Africa and southern South America bears the hallmarks of La Nina, as does the above average rainfall in Southeast Asia.”
Illinois State Climatologist Trent Ford said La Nina winters in Illinois tend to have a mild start.
“Because of those mild temperatures, we don’t have a tremendous amount of snow, and then they tend to be backloaded, so all of the winter weather that people prepare for tends to come in the latter part in January and February, maybe even into March as opposed to the first part,” Ford said.
Temperatures across parts of Illinois last year were 7 to 10 degrees warmer than normal, making it one of the warmest Decembers on record. It was over 50 degrees in Chicago on Christmas Eve.
The warmer conditions made the atmosphere ripe for storms on Dec. 10, 2021, when an EF-3 tornado touched down in Edwardsville, causing a warehouse to collapse, killing six workers.
Ford said the La Nina weather pattern may mean more precipitation this winter for some areas of the state.
“For at least the southern half of Illinois and much of the southern part of the Midwest, it is wetter than normal in wintertime,” Ford said.
For the rest of the country, La Nina results in colder temperatures in the northwestern part of the U.S. In the southwestern part of the country, it means rain clouds are pushed out to sea, creating a drier climate.