Weather Insider: La Nina Update – September 2025
La Niña and El Niño are two phases of a larger climate cycle known as ENSO, or the El Niño Southern Oscillation. ENSO is just one of many different climate cycles across the globe. Whether temperatures in certain regions of the equatorial Pacific are warmer or cooler than average determines the phase we are in. There is also a neutral phase, which we are currently in. El Niño represents when waters are warmer than average, and La Niña is when those waters are cooler than usual.
During LA Niña events, like the one that may develop this fall, the jetstream tends to get pushed farther to the north. This tends to keep more winter systems, like atmospheric rivers, to the north. This tends to lead to drier and warmer winters for Southern California. Conversely, cooler and wetter weather is more likely for the Northwest and northern tier of the country.
The La Niña Watch in the latest report from the Climate Prediction Center means that we are likely to transition to La Niña in the coming months. They give a 71 percent chance of this happening between October and December. Into next year, La Niña is still favored, but only with a probability of 54 percent.
