A very strong El Niño significantly increases the likelihood of a wetter-than-average winter in California. This is due to the way it alters atmospheric conditions, steering more storms toward the state. However, the type of precipitation—rain versus snow—can vary. While snowpack in the Sierra Nevada mountains acts as a natural reservoir, providing water gradually as it melts, warmer conditions associated with El Niño may lead to more rain than snow, which runs off quickly and is harder to store.