What is a primary factor that influences the weather during El Niño?

The primary factor that influences the weather during El Niño is oceanic surface temperature changes. During an El Niño event, the surface water temperatures in the central and eastern Pacific Ocean rise significantly compared to normal conditions. This warming alters atmospheric circulation patterns, disrupting the usual weather patterns across much of the globe.

As the warm ocean waters release heat into the atmosphere, it affects wind patterns, precipitation distribution, and can lead to extreme weather events such as increased rainfall in some regions and droughts in others. Understanding the role of oceanic surface temperatures is crucial, as they serve as a driving force for many of the climatic changes associated with El Niño.

While atmospheric pressure differences do play a role in the manifestation of El Niño and can be a consequence of the changes in sea surface temperatures, the primary driving factor is the warming of the ocean itself.