The 2026 El Niño winter impact is now the focus for meteorologists watching a forecast that could rank among the strongest in modern record. That matters because a very strong El Niño can shift winter weather across the U.S. and may also affect the polar vortex.
Amy Butler on the vortex
Amy Butler said, “El Niño tends to weaken the vortex in mid-to-late winter.” She is a physicist at NOAA's Chemical Sciences Laboratory, and her point puts timing at the center of the outlook: the biggest effects may not arrive right away.
El Niño tends to bring wetter-than-average conditions across the South, while the Great Lakes, interior New England and the Pacific Northwest tend to see less snow. A stronger event can also create more surprises by pushing and pulling on other large climate forces that shape winter patterns.
Judah Cohen and the jet stream
Judah Cohen, a polar vortex expert at MIT, said scientists do not yet fully understand how El Niño and the polar vortex interact. The worry is not just the El Niño signal itself, but how it might work with the jet stream and the lower atmosphere to change where cold air and precipitation end up.
The polar vortex is a wintertime phenomenon, a large area of cold air high up in the atmosphere that normally spins over the North and South poles. The vortex above the Arctic is linked to the jet stream, and both can be impacted by El Niño because El Niño drives changes in high- and low-pressure patterns in the troposphere, the lowest layer of Earth's atmosphere where weather happens.
That setup can matter most when the vortex weakens. A strong polar vortex is generally associated with milder winter weather, while a weak one often lets cold air funnel south from the Arctic into the central and eastern U.S. When the vortex gets disrupted, it can also influence precipitation and send very cold air into locations in the Eastern U.S.
What NOAA is watching
NOAA says the El Niño developing along the equator in the Pacific is forecast to be “very strong.” Stronger El Niño events tend to have greater interactions with other strong planetary climate forces, and they can increase the chances for sudden warming events in the stratosphere that affect the surface for several weeks.
Scientists say the relationship is still not fully understood, even as they warn that the combination could shape winter weather. El Niño tends to weaken the polar vortex in mid-to-late winter, but if the vortex stays strong, the winter should tilt milder overall, except possibly along the West Coast.
The readers most likely to feel the biggest change are in the South, the Great Lakes, interior New England and the Pacific Northwest, with the Eastern U.S. also in the zone where a disrupted vortex can steer cold air south. Which U.S. regions end up on the sharper edge of that pattern will depend on how the polar vortex behaves as winter develops.
