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 stubborn high pressure system currently squatting over the Great Australian Bight is the main culprit for rising temperatures across country SA.
The weather bureau is warning residents in north Queensland to prepare for heavy downpours, flash flooding and thunderstorms.
Perth is heading for a scorching 40 degrees Celsius on day one of a heatwave that is expected to last for at least five days.