There isn’t a one-size-fits-all approach to forecasting climate patterns when there’s an El Niño or a La Niña pattern in place. 

What You Need To Know

  • La Niña means cooler ocean tempeatures

  • Low-end moderate La Niña pattern this winter

  • La Niña tends to run drier in SoCal, but not always

  • No guarantee this winter will be dry

What Exactly is La Niña?

El Niño and La Niña patterns are part of the El Niño Southern Oscillation, which monitors sea-surface temperatures in the equatorial Pacific Ocean. 

When sea-surface temperatures in this region are above average, it’s called El Niño; when they are below average, it’s called La Niña. 

We aren’t talking about major changes in water temperatures but typically more minor swings — usually on the order of plus or minus a degree Celsius — 1.8 degrees Fahrenheit — or less.

There are instances when water temperatures have been as much as eight degrees Fahrenheit above average — a very strong El Niño — but it’s not common.

This Winter's Forecast

This year, the prediction is for a low-end moderate La Niña — 1.1 degrees Celsius above average. This pattern emerged in August 2020 and is forecast to continue through the winter. 

Courtesy: NOAA.

La Niña: No Sure Thing

Some people — even forecasters — erroneously equate La Niña with drier-than-average conditions here in Southern California. In reality, there are no hard-and-fast rules to climate impacts during either El Niño or La Niña, and anyone who says differently is simply wrong.

Of all La Niña patterns on record — 22 events in all — Southern California has received, on average, 76% of its normal rainfall.

Courtesy: Jan Null of Golden Gate Weather.

But there have been some stark contrasts in La Niña years, even over a short period of time.

The 2016-2017 weak La Niña brought above-average rainfall to Southern California, 118% of average. 

Courtesy: Jan Null of Golden Gate Weather.

Just one year later during the winter of 2017-2018 in another weak La Niña pattern, Southern California received well below-average rainfall, 44% of average.

Courtesy: Jan Null of Golden Gate Weather.

Of the 22 La Niña events on record, seven have brought near-average (85%+) or above-average precipitation to Southern California—so 32% of the time. That means 68% of the time when there is a La Niña set-up, we have below-average rainfall—but that’s still not a guarantee. 

NOAA's Climate Prediction Center does takes these odds into account when issuing their winter outlook. They are calling for a 40 to 50% of below-average precipitation this winter in Central and Southern California — clearly, not a slam dunk. 

So even though the odds may be in favor of a drier winter during a La Niña pattern, it is not a sure thing. We’ll just have to wait and see.