The interaction between El Niño and the polar vortex could lead to extreme winter weather in parts of the U.S. and Europe. A weakened polar vortex may funnel Arctic air southward, increasing the likelihood of severe cold spells and heavy snowfall in the eastern U.S. and mid-Atlantic regions. Conversely, a strong polar vortex could result in a milder winter overall. Scientists caution that the strength of this El Niño, combined with ongoing climate change, adds uncertainty to forecasting its full impact.