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.
A cold front has brought damaging wind gusts to parts of Victoria with more on the way.
Weather records for seven Queensland regions have been re-written, with Saturday's unseasonable temperatures setting the new benchmark for the hottest July day in seven locations, the Bureau of Meteorology says.
Residents are warned to take care outdoors as snow, hail and wind gusts send Tasmania into a big chill.