After three consecutive winters dominated by the La Niña weather pattern, we’re now a few weeks into an El Niño winter, which state climatologist Justin Glisan says could very well mean significant changes ahead for Iowa’s weather.
“We’re in a moderate-to-strong El Niño and we have a 54% chance of this being a historically strong El Niño, meaning, exceedingly warm sea surface temperature anomalies,” Glisan says. “When we look at wintertime conditions for El Niño, we typically see warmer temperatures through December, January, February.”
That falls in line with what happened in Iowa last month, as snowfall during December was far below normal in what’s usually the snowiest month of the year. Plus, Glisan says, December concluded nine-degrees warmer than average statewide.
The last El Niño was in 2019 and Glisan says there’s a consistent pattern over the decades.
“If we look back at strong El Niño events, going back to 1950, we’ve had seven,” Glisan says. “Six of those, we’ve seen generally wetter conditions across the state.”
Iowa has been mired in drought for more than three-and-a-half years, and Glisan says we experienced what he calls a “snow drought” during December, while a shift could be coming in the weeks ahead.
“In El Niño and strong El Niños, we generally see below-average snowfall across much of the state, but not necessarily drier conditions,” Glisan says. “We see more rainfall, we see more wintry mix-type of precipitations. So if you couple that together with the 30-year trend, there is a potential for wetter conditions through winter along with those warmer temperatures.”
From year to year, Glisan says the average temperature over 365 days usually doesn’t even vary by one degree, up or down, but 2023 ended more than two-degrees warmer than the norm in Iowa, putting it in the state’s top 20 warmest years on record.