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.
The heaviest August rain in decades turned central Australia into an eerie place this week, causing waterfalls and thick fog.
Winter Wonderlights delivered a Christmas in July present to Ballarat tourism, with a 50 per cent increase in visitors to the region during the coldest month of the year.
An impending rain event scheduled for the opening days of spring continues the pattern of wet weather which has gripped eastern Australia during winter.