Monthly sea surface temperatures using the Nino 3.4 Index. The Nino 3.4 index is a measure of the temperature of the surface of the central tropical Pacific Ocean, and is used as the standard metric in this context. As of June, the temperature of the ocean surface was 0.8 degrees Celsius higher than the long-term average (1950??022). This is comfortably above the El Nino threshold of 0.5 degrees Celsius. For the period of April??June 2023, the three-month average Nino 3.4 Index was 0.5 degrees Celsius. To qualify as an El Nino year, this average must meet or exceed the threshold for at least 5 three-month periods.