What is La Nina, and How Will it Impact Winter Weather?


Heading into winter, you might occasionally hear about “La Nina,” a weather condition that can occur over the Pacific. The condition, which is Spanish for “little girl,” refers to a cooling of the waters of the Pacific. This cooling occurs, on average, once every four or five years. When it does, it often has consequences for much of the US heading into Winter.

You might be wondering, how, exactly, some cold water over the Pacific can affect winter weather in a country as large as the US. That’s what we’re here today to discuss. So, what is La Nina, and how might it affect the weather for the next few months? Read on to find out.

What is La Nina?

La Nina is the name given to a periodic cooling of the Pacific Ocean. The cooling comes around somewhat regularly, happening, on average, once every four or five years. The cooling of the water around the equator is, in and of itself, not the sole determiner of the weather. However, it does factor in to the atmospheric conditions that create the weather in this hemisphere.

Typically in the winter, La Nina causes a pattern in the subtropical jet and the jet stream that causes cool air to stir off of the coast of Western Canada. The northern US gets buffeted with driving winds from the jet stream as it joins with the subtropical jet, and the two tend to plunge southward into the Eastern US as they travel west-to-east.

What Does This Mean for the Weather?

Generally, patterns defined by a La Nina cooling period result in some predictable conditions in the US. The Northwest tends to experience particularly wet weather, more so than usual. The Northern Plains experience very cool weather, bringing snowfall and blizzards.

The regions around Southern Michigan, Illinois, West Virginia, Kentucky, and Southeastern Missouri tend to experience wet conditions in this pattern, as well.

Meanwhile, the Mid-Atlantic, ranging from as far north as western New York to as far south as northern South Carolina experiences warmer than average conditions.

Those warm conditions are often experienced far to the west, as well, ducking under the wet conditions near the Great Lakes and bringing warmer than average weather to northern Georgia, southern Tennessee, northern Alabama, northern Mississippi, the middle of Arkansas and parts of Oklahoma.

The main conditions felt in the southern half of the country during a La Nina period are extremely dry. The band from Southern California, all the way to the East Coast in southern South Carolina, and as far south as the middle of Florida, experiences these dry conditions.