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 couple of scorchers are on the way for Adelaide, Melbourne, Canberra and Sydney over the next few days.
Following a good start to January 2017 rainfall, when 125mm fell during the first 48 hours of the year, conditions have been relatively dry for the Northern Territory capital.
In the early hours of the morning, Brisbane had its warmest minimum temperature since at least 1999, when the mercury halted its descent at 28 degrees just after 3am.