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 town of Gawler and surrounding districts north of Adelaide are bracing for significant flooding, with the Army called in to help residents fill sandbags at Two Wells.
Three adults and two young children have been rescued by helicopter after becoming trapped in floodwaters in Huonville, south-east of Tasmania.
Water levels are rising in the Gawler River, with significant flooding expected as it reaches its peak later tonight.