Will El Niño bring snowy weather to Pennsylvania this winter? Here’s what experts predict
Fall has finally arrived following months of record-setting summer heat. As Pennsylvanians begin looking toward winter for cooler air and seasonal storms, is relief on the way?
Perhaps not as strongly as some might hope, according to experts at the National Oceanic Atmospheric Administration’s Climate Prediction Center. The agency largely expects El Niño, a climate pattern representing abnormal conditions in the Pacific Ocean, to produce a winter of warmer, drier weather for much of the northern U.S.
As we head closer to winter, here’s what experts say could be in store for Pennsylvania.
What is El Niño?
El Niño and its counterpart, La Niña, are two opposing climate patterns that represent abnormal conditions in the Pacific Ocean.
Under normal conditions, trade winds in the Pacific Ocean blow west along the equator and bring warm water from South Africa toward Asia, NOAA writes. Through a process called upwelling, colder water rises from the ocean’s depths to replace that warm water.
When an El Niño pattern is present, though, those important trade winds weaken. So, warmer water is instead pushed back east to the western coasts of North and South America, NOAA says.
El Niño’s effects can significantly impact weather. Warmer waters in the world’s largest ocean can alter jet streams and climate systems that work to regulate temperatures, rainfall and severe weather throughout the U.S. and other parts of the world. El Niño patterns can also reduce the availability of cold, nutrient-rich water in the Pacific Ocean that underwater ecosystems need to thrive.
The name El Niño, which translates to “little boy” in Spanish, was coined by South American fishermen in the 1600s who were among the first to notice the oceanic pattern. The full name those fishermen used was “El Niño de Navidad” because the pattern typically peaks around December, NOAA writes.
What does El Niño mean for Pennsylvania this winter?
According to the Climate Prediction Center’s most recent report on El Niño’s evolution, status and predictions, much of the northern U.S. can likely expect a warmer, drier winter this time around.
The agency predicts nearly all of Pennsylvania is leaning toward observing above-average temperatures in October, November and December. Portions of the Northeast, Pacific Northwest and Alaska are the most likely to record a warmer winter season, according to the latest seasonal temperature outlook issued Sept. 21.
Many southern states, including much of the Sun Belt, are expected to observe above-average precipitation rates entering the winter. Some portions of southeast Pennsylvania, including Philadelphia, are leaning toward a wetter-than-average late fall and early winter, while the Keystone State’s northwest regions may observe below-normal precipitation.
NOAA warns outlooks predicting above-average temperatures do not mean northern states will never see snow. In fact, data from the late 1940s through 2015 found five of the snowiest winters in Harrisburg, Pennsylvania’s capital, occurred during El Niño winters, the National Weather Service found.
Regardless, estimations of warmer temperatures in the coming months may seem disappointing for winter weather lovers considering Pennsylvania’s recent snowfall trends.
Snowfall in the State College area, for example, already fell well below expectations last winter, according to NWS archives. The 2022-23 winter season produced roughly 24.3 inches of snowfall, falling short of the 39.4 inches expected in an average year. The 2019-20 winter season produced about 12.1 inches of snow, marking the lowest observed rate since at least 1893, the earliest year on record through the NWS.
Hurricanes rarely pose a direct threat to Pennsylvania, and that trend may continue this fall. El Niño generally emboldens hurricane activity in the central and eastern Pacific basins while suppressing activity in the Atlantic basin, NOAA writes. So far, the Atlantic Ocean has produced at least 15 named storms throughout this hurricane season, which runs through Nov. 30.
How long will El Niño stick around?
In its most recent report on the subject, the Climate Prediction Center estimated El Niño is expected to persist throughout the North Hemisphere’s winter season. The agency estimates there’s roughly a 95% chance the pattern continues into late winter and early spring next year.
Traditionally, episodes of El Niño and La Niña last between nine and 12 months, but more extreme instances can linger for years. These events generally occur on an irregular schedule about every two to seven years, NOAA reports.
El Niño events are more common than La Niña. During La Niña, colder waters in the Pacific Ocean push jet streams north, leading to drier weather in southern states, warmer weather in northern states and, potentially, increased hurricane activity.
The National Weather Service’s State College office has not yet responded to a request for comment on El Niño’s potential impacts on central Pennsylvania this fall and winter.
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