The National Ocean Service says trade winds blow warm Pacific Ocean water west toward Asia in normal climates. The El Niño climate pattern occurs when trade winds diminish, causing warm water to return to the Americas.
The warmer water stretches the Pacific Jet Stream south, making sections of the northern U.S. and Canada drier and warmer than normal while increasing precipitation in the south and north.
Unusual winter weather may impact winter tourism. Snowfall in Montana, which is projected to be below average, may decrease ski resort attendance, while Utah and Colorado may see an increase.
Winter storms may impact airline travel, and El Niño may intensify storms in specific places. Check the National Weather Service website for active weather alerts.
Consider having a backup plan in case of rescheduling your vacation in locations expected to receive more precipitation due to El Niño.