Meteorologists with the National Oceanic and Atmospheric Administration (NOAA) have detected unusually cold ocean waters in the Pacific near the equator.

The National Weather Service officially announced La Niña's return on Thursday, saying it has a 65- to 75-percent chance of continuing through the upcoming winter.

So what is La Niña? And what does that mean for us?

La Niña is basically the opposite of its more recognized sibling, El Niño.

It is often associated with winter, and brings different types of weather to different parts of the United States and North America. But remember, La Niña doesn't mean a specific change is going to happen throughout a given season; it simply means the odds of these changes are increased.

If you look at NOAA's sea surface temperature contour chart for the equatorial Pacific Ocean, you see quite a bit of blue, meaning it's getting chilly.

La Niña will typically bring cooler, wetter weather to the Pacific Northwest and sunny, warm and dry weather to the Southwest -- so both regions play a bit to their strengths. It also brings some dry weather to the southeast and can mean the Northeast gets some cold snaps, plus an increase in precipitation (read: snow).

La Niña's typical effects on the United States.

NOAA says La Niña and El Niño occur about every 3-5 years, and it's not clear-cut how long they last -- it depends entirely on how the ocean water temperatures compare to normal at a given time of year.

For more answers on La Niña, visit NOAA's frequently asked questions page for the phenomenon.