Ellie Park, Multimedia Managing Editor

In October, the National Oceanic and Atmospheric Administration, or NOAA, released winter weather predictions, forecasting a 23 percent chance of above-normal temperatures in New Haven.

The News spoke to NOAA’s Matthew Rosencrans, lead meteorologist at the Climate Prediction Center, to explain what this number means for Connecticut. 

“In Southern New England, nine of the last 10 years have been above the average temperature, and five of the last 10 have been in the ‘above normal’ category,” Rosencrans said. 

The upper third of recorded winter averages are considered above normal. According to Rosencrans, winter 2025 will continue this decade-long trend of warm winters. 

To make his prediction, Rosencrans examined precipitation patterns, which will be below normal in 2025. And what precipitation does occur will fall as rain, not snow. 

“That’ll just wet things up, but it won’t create a snow cover, which typically creates a feedback with cold temperatures.” 

Warm temperatures will cause less snow. Less snow will trigger warmer temperatures. The combination sets up a feedback loop. 

Yet a predicted high average temperature does not mean New Haven will be warm all winter. Averages conceal some variation. 

“The average temperature for Southern New England will be 30.0 to 30.07 degrees Fahrenheit, but that’s when you average daily highs and nightly lows for all 92 days of winter,” Rosencrans said. “There will be periods of cold. There will be periods that will be very warm. It doesn’t mean that it’s going to be all one way.”

Rosencrans’ forecast is only about a degree above normal –– but for heating systems, energy companies and organisms alike, this variation has consequences, he said.  

Like humans, animals and plants slow down in winter. David Vasseur, professor of ecology and evolutionary biology, explained that organisms typically have slower metabolism during these months to conserve limited resources. Short, warm winters send mixed cues. 

“Individuals burn through their energy reserves more rapidly,” Vasseur said, which can decrease the organisms’ chance of survival. 

And, more critically, different species that rely on each other may not respond to these unnatural cues in the same way. 

“The timing of species emergence, dormancy, migration or reproduction are no longer well matched to the availability of food,” Vassuer said. 

This misalignment is called phenological mismatch.

Take birds and caterpillars: emergence from cocoons used to occur during bird hatching season, when parents needed large amounts of food. Today, caterpillars emerge much earlier. Birds lack food when they most need it, and plants have to cope with overwhelming herbivory from hungry, un-hunted caterpillars. 

It’s as though species are experiencing seasonal jet lag, adjusting to new time zones with earlier waking cues –– cues that their food source may or not respond to.

Phenological mismatch is a major challenge for Connecticut’s ecosystems, David Post, professor of aquatic ecology at Yale, told the News. 

“That’s always been one of the big concerns about climate change –– not so much the mean temperature changing, but the variance, and how the variance and the timing of events would change,” Post said.

Scientists have known since the 1980s that winters were getting shorter and warmer, Post said. Some effects are obvious: fish spawn earlier, insects emerge earlier and lakes that were once used for ice fishing no longer freeze at all. 

Post’s research, too, is impacted by these changes. 

“We rarely can sample those lakes in winter anymore. They just don’t freeze,” Post said. 

To begin with, winter is an understudied season. 

In the midst of increasing temperatures, it’s become both more difficult and more necessary to study. 

“It was thought that it was a period when the ecology of, say, a lake, was reset for the next summer,” Post said. “What that misses is that what happens in the winter influences the growing season in very profound ways.”

Post studies the ecology of frozen lakes, and explained that research on winter ecology has only emerged in the last 10 to 20 years. 

Ecologists are now studying forests and lakes during winter, chronicling the impact of snow cover on factors like tree growth and plankton abundance. 

 “It is just not a time of year that ecologists have studied very much. And so there will be surprises. We don’t really know the long-term impacts on a lot of ecosystems.” 

For example, Vasseur wonders if longer summers and growing seasons can compensate for organisms’ increased use of energy during warm winters.  

Connecticut’s winters are changing. Temperatures this season will be above normal, falling in line with the decade-long trend of warm winters. 

Rosencrans still encourages residents to prepare for snow storms and power outages this winter by refreshing storm kits with three days worth of water and packaged food, as well as rechargeable batteries and a NOAA weather radio. 

“That’s what we want: people to stay safe no matter what the forecast is.” 

Rosencrans’ national winter weather predictions can be viewed here.