La Niña: What it is and how it could affect winter weather in 2024

Everything is connected. The surface temperature of the tropical Pacific Ocean can influence weather patterns around the world. If this temperature cools as part of a La Niña pattern, the U.S. can expect colder and rainier conditions in the north and warmer and drier conditions in southern states. This can affect everything from snow days to heating costs. Let's take a look at what's going on with a predicted La Niña event this winter.

Get to know ENSO

If you spend time around weather people, you may come across the abbreviation ENSO. This stands for El Niño-Southern Oscillation.

“ENSO is one of the most important climate phenomena on Earth because it can alter global atmospheric circulation, which in turn affects temperature and precipitation around the world,” explains the National Oceanic and Atmospheric Administration.

ENSO includes both La Niña (the girl) and El Niño (the boy), but there is also a third phase: neutral. ENSO is a natural cycle that moves between these states. According to NOAA, we are in a neutral phase, but scientists expect a weak La Niña to develop this fall.

What is La Nina?

La Niña and El Niño are naturally occurring climate patterns. A La Niña event refers to the cooling of sea surface temperatures in a specific region of the Pacific Ocean, the central and east-central equatorial regions.

“Typically, a La Niña is preceded by an accumulation of cooler-than-normal groundwater in the tropical Pacific,” NOAA says. “Then the easterly trade winds strengthen, the cold upwelling off the west coast of South America and along the equator intensifies, and sea surface temperatures fall below normal.” That's the recipe for La Niña.

Jet streams are high-level air currents that move from west to east. Jet stream winds help direct storm paths and also act as a boundary between warmer (to the south) and colder (to the north) air masses.

“The position of the jet, and therefore the boundary, has a strong influence on temperatures near the ground,” climate scientist Tim Woollings wrote in a NOAA statement.

La Niña is pushing the jet stream—and the storms it guides—northward. La Niña occurs every few years and can last for several years. The impact on the weather is greatest in the winter months. As it sets in this year, expect wetter conditions across the Pacific Northwest with hotter than normal temperatures across the southern United States.

What is El Niño?

El Niño is the flip side of La Niña. Recent extreme heat conditions can be attributed to the climate crisis. El Niño – the part of the ENSO cycle where surface temperatures of the equatorial Pacific Ocean are above average – also played a role. An El Niño event typically brings wetter conditions to the southern United States and warmer, drier conditions to the north. El Niño typically lasts shorter than La Niña.

Will there be La Niña in 2024?

The National Weather Service predicts a 60% chance of La Niña developing sometime in November. It is expected to be a weak event when it occurs.

Historically, La Niña events that occur this late in the year tend to be weak.

“The strength of an ENSO event, as measured by sea surface temperature deviations, is important because stronger events change atmospheric circulation more consistently, leading to more consistent impacts on temperature, precipitation, and other patterns,” researcher Emily Becker wrote in an October ENSO -Update for NOAA. This leaves room for forecast changes as we approach the end of the year.

The NWS Climate Prediction Center released seasonal forecasts for November through January that show a chance of above-average temperatures for the southern and eastern regions of the United States. Watch for below-average rainfall stretching from coast to coast in the south. Northern parts of the country could experience above-average rainfall. This is in line with expectations for a weak La Niña.

We are currently in a La Niña watch. Expect an official ENSO update in mid-November. At this point, we may have a better idea of ​​whether you should invest in a new umbrella, stock up on warmer workout clothes, or plan to water your lawn more often this winter.