The last El Niño was the 2023–2024 event. It began developing in mid-2023, peaked in late 2023 to early 2024, and faded out by May 2024.

Timing

  • El Niño conditions were present by June 2023.
  • The event strengthened through July–August 2023 and reached moderate strength by September 2023.
  • NASA reported that it died out in May 2024.

In plain terms

So, if you mean the most recent El Niño, the answer is May 2024 for when it ended, with the event itself running from 2023 into 2024.

Quick note

El Niño is a recurring climate pattern, so another one can happen later, but the latest completed one was the 2023–2024 event.