The NINO3.4 index is one of several El Niño/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 Niño 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 Niño or La Niña event is identified if the 5-month running-average of the NINO3.4 index exceeds +0.4°C for El Niño or -0.4°C for La Niña for at least 6 consecutive months.
Top End residents are unlikely to be relieved of the oppressive hot and humid build up conditions until Christmas, because the rain-bringing La NiÃ±a weather pattern is unlikely to eventuate in coming months, the Bureau of Meteorology has warned.
An international tourist has died and a woman has been injured after being hit by lightning while camping at Mt Warning, on the NSW north coast, police say.
The opening week of summer has been a hot and thundery mix in New South Wales and there is more to come.