El Niño is intensifying and could have an interesting influence on winter weather in the U.S., including a weird upside-down temperature pattern from December through February.

What is El Niño?

El Niño is a warming of water in the central and eastern Pacific Ocean near the equator that typically happens every three to four years.

(MORE: Your complete guide to El Niño)

But this won't be an ordinary, average El Niño. It's likely to flirt with or shatter the all-time record strongest El Niño.

That's measured by the relative oceanic niño index, or RONI.

It's a three-month average of how far above or below average water temperatures are near the equator in the eastern Pacific Ocean relative to the rest of the tropical ocean used to track El Niño, in degrees Celsius.

Get More of Our News on Google

Set The Weather Company as a 'Preferred Source' to get quicker access to the news you value.

What is a typical El Niño winter pattern?

El Niño is only one of several influences on weather patterns in the U.S., particularly in winter.

However, given its expected strength, it's more likely it will leave its thumbprint on winter's weather, much as it's already doing to the hurricane season.

The usual El Niño is warm in parts of the North, wet along much of the South, and dry in parts of the Ohio Valley.

That's because the southern branch of the jet stream, called the subtropical jet, is strong in El Niño winters. That often steers storms across the nation's southern tier from California to Florida and the Southeast.

What about this is 'upside down'?

Admittedly, we're using the phrase "upside down" a bit tongue-in-cheek.

Don't worry, snowbirds. It doesn't mean Florida's winter will somehow be colder than, say, Nebraska.

It means that much of the northern U.S. tends to trend warmer than average in winter during a bullish El Niño while the southern U.S. is either near or somewhat cooler than average.

You can see that in the map below, which shows all previous El Niños with at least a RONI of +2 degrees Celsius, indicative of the strongest El Niños since 1950.

And as we alluded to earlier, it's only because the South trends wetter during these El Niño winters that it isn't warmer in winter, as the map below shows. Stronger El Niños have also been wetter along much of the West Coast, not just California.

(MORE: These hurricanes didn't care about a super El Niño)

What does this mean this winter?

• One other influence on winter weather is when a blocking pattern sets up that unleashes colder air deep into the central and eastern U.S. for a week or more. It's not clear yet how much that blocking pattern may set up this winter, but it could do so later in winter.
• Expect a warmer winter in the northern U.S., particularly the Northern Plains and upper Midwest.
• While winter is typically Florida's dry season, expect it to be wetter than usual this season. Tornadoes are a good likelihood, too.
• Given the wetter South tendency, there could be an increased threat of snow and/or ice from the Southern Plains to the Southeast this winter, if just enough cold air happens to be in place.

(MORE: How El Niño could impact snowfall)

Jonathan Erdman is a senior meteorologist at weather.com and has been covering national and international weather since 1996. Extreme and bizarre weather are his favorite topics. Reach out to him on Bluesky, X (formerly Twitter) and Facebook.