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.
The Top End of the Northern Territory is having one of its hottest May's on record, which is causing issues for a number of mango plantations.
Whilst it may just be beginning to feel like winter across the southern capitals, it sure feels like the tail-end of summer in Darwin.
Eight areas across New South Wales experienced record-breaking cold weather overnight, but the Bureau of Meteorology (BoM) says the state is still set for a relatively warm winter.