The NINO3.4 index is one of several El Niņo/Southern Oscillation (ENSO) indicators based on sea surface temperatures.
NINO3.4 is the average sea surface temperature anomaly in the region bounded by 5°N to 5°S, from 170°W to 120°W. This region has large variability on El Niņo time scales, and is close to the region where changes in local sea-surface temperature are important for shifting the large region of rainfall typically located in the far western Pacific.
An El Niņo or La Niņa event is identified if the 5-month running-average of the NINO3.4 index exceeds +0.4°C for El Niņo or -0.4°C for La Niņa for at least 6 consecutive months.
South Australians are waking to assess the damage amid rising floodwaters, after two nights of severe weather that battered much of the state.
Holiday-makers were evacuated from their cabins and caravans in the middle of the night at a Barossa Valley caravan park after a nearby river broke its banks.
Winds sweeping South Australia have plunged thousands of residents into darkness again for another night only a day after the entire state suffered a blackout.