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.
Much of the state has seen great rainfall over winter, with only the north and central coast missing out.
Snow has fallen in Western Australia's Stirling Ranges, including Bluff Knoll, for the second time in a matter of weeks, after a chilly night in the Great Southern.
Amateur photographers have been all too happy to bid farewell to winter in stunning style, capturing picture-perfect shots of the first day of spring from around the country.