The National Oceanic and Atmospheric Administration (NOAA) predicts another warm and dry winter in California due to a third consecutive year of La Niña conditions in the Pacific Ocean.

One of the major factors influencing weather in the United States and other countries, particularly in the late fall, winter and early spring, is the La Niña climatic pattern— a natural cycle characterized by cooler-than-average ocean water in the central Pacific Ocean.

In contrast to the more well-known El Niño, which occurs when the Pacific Ocean’s water temperature rises above average, La Niña means “little girl” in Spanish, whereas El Niño means “little boy.”

Trade winds are even stronger than usual during La Niña, bringing more warm water into Asia. Upwelling increases off the west coast of the Americas, sending cold, nutrient-rich water to the surface. The jet stream is forced northward by the cold seas in the Pacific, which has an impact on weather patterns both domestically and internationally.

Since the colder waters force the jet stream north, a normal La Niña winter in the United States delivers cold and snow to the Northwest and particularly dry conditions to the majority of the southwestern part of the country. Although every La Niña winter is unique, they often favor below-average precipitation in the Southwest of the United States. Much of the west, including Colorado, Utah, and California have only sporadic relationships between precipitation levels and La Niña winters.

While La Niña is expected to bring a warm and dry winter season, winter forecasts are inherently uncertain since so many factors in the atmosphere are not predictable months or even weeks in advance. Climate change is also adding to seasonal outlooks’ complexity.

Sometimes, La Niña winters can bring more precipitation than average across nearly the entire Western United States, with recent examples including ‘07-08, ‘10-11, and to some extent ‘16-17. However, the past two winters (which were both La Niñas) had low precipitation levels across most of the West.

According to the San Diego County Water Authority, every La Niña year has recorded less rainfall in San Diego than on average. In 2016-17, a La Niña year, San Diego county recorded 8.1 inches of precipitation, while the average amount of annual precipitation is 12 inches.

For Southern California, a hot and dry winter is not what is needed amid concerns about a drought. As there have been heatwaves and wildfires throughout the state, any coming precipitation is desperately needed.