This year’s potentially record-setting El Niño is expected to shape winter weather and snowfall across the US. A new CNN Weather analysisshows how snowfall has changed during El Niño winters, offering clues as to what to expect this season.

El Niño is a natural climate pattern marked by unusually warm water in the central and eastern tropical Pacific Ocean. That extra warmth changes rainfall and atmospheric circulation patterns, with effects on weather that extend far beyond the Pacific.

El Niño’s influence on US weather is strongest in winter, when the jet stream — a fast-moving current of air that helps steer storms — typically shifts south and extends east across North America. That change favors wetter conditions across the United States, while much of the north tends to be drier and experience milder temperatures.

But a wetter winter is not necessarily a snowier one. Snowstorms need sufficiently cold air, so if temperatures are too warm for snow, an increase in precipitation just means more rain.

To get a sense of what El Niño’s impacts can look likeCNN Weather analyzed January-through-March snowfall from 1959 through 2026. The maps below show how past El Niño winters varied from average after controlling for long-term changes in snowfall. They describe historical relationships, rather than predicting this winter’s snowfall.

During past El Niño winters, snowfall was generally above-average across the southern US, stretching from parts of the Southwest and southern Rockies through the southern Plains, southern Appalachians and Mid-Atlantic.

Storms that affect the Mid-Atlantic’s snow chances typically take a track along the spine of the Appalachians or push off the coast and become nor’easters.

These nor’easters are “juiced” by El Niño, according to Jon Gottshalck, chief of the Operational Prediciton Branch of NOAA’s Climate Prediciton Center and lead forecaster for the agency’s winter outlook this year. “They’re very strong, energetic and they’re very wet,” Gottshalck said. This could bring above-average snowfall to places like Washington, DC, and Baltimore.

Even though the Northeast typically misses out on snow during a strong El Niño winter, all it takes is one massive storm to skew snow totals for the whole season.

Parts of the Pacific Northwest, northern Rockies, Great Lakes and Interior Northeast saw less snow. The shift in storm tracks can leave some northern areas with fewer opportunities for snow, and warmer conditions can also make storms more likely to bring rain.

But remember: This is relative to each location’s average, not a measure of which places get the most snow. So in the South, where snowfall is typically scarce, even a large percentage increase well above average snowfall can still amount to a small total on the ground.

This year’s El Niño is set to be one of the strongest on record. A stronger El Niño increases the likelihood of its typical effects, Gottschalck said.

But it does not necessarily produce a larger increase in rain or snow at a particular location than compared to a weaker event. and Gottschalck noted there are also relatively few strong El Niño events in the historical record to draw firm conclusions from.

An average alone can also be misleading. A few exceptionally snowy winters can pull the totals upward, even if many other winters fall short.

To see where snowier El Niño winters were more common, CNN Weather also examined how often snowfall finished above average during El Niño those years.

Above-average snowfall occurred in more than half of the El Niño winters analyzed across parts of the Southwest, lower Midwest, southern Appalachians and iInterior Northeast. Much of the Pacific Northwest, northern Rockies and parts of the Great Lakes had below-average snowfall more often than not.

And in a moderate-to-strong El Niño, like this year’s super El Niño, those differences grow. Places that typically see above-average snowfall during an El Niño tend to see even more frequent snow during a strong El Niño, while places that typically see less tend to have snow even less frequently.

The wide spread in totals in cities across individual El Niño winters illustrates how El Niño only offers a rough guide to how snowy an individual winter could be.

For December through February, NOAA’s outlook favors warmer-than-average temperatures across much of the northern and eastern US.

The Pacific jet stream will be “floodingNorth America with Pacific Ocean air,” Gottschalck said. That milder ocean air should make prolonged Arctic outbreaks harder to sustain, although shorter bursts of cold remain possible.

One wild card is how atmospheric circulation patterns over the Arctic and North Atlantic evolve. Changes there can allow cold air to spread into the eastern US and alter the paths of storms, even under a strong El Niño.

A persistent pattern favoring cold could disrupt the expected mild winter across the north, Gottschalck said. But forecasters cannot reliably predict in October when those episodes will occur or how long they will last.

The timing of the cold air will become clearer much closer to individual storms, he said. Even in a generally mild winter, a brief cold spell that coincides with a powerful coastal storm can make a big difference in a season’s snowfall.

During the very strong 2015-16 El Niño, New York City had one of its warmest winters on record according to the National Weather Service. Yet the January 2016 blizzard dropped 27.5 inches in Central Park, setting the city’s single-storm snowfall record.