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.
Victoria has been spared the brunt of the wild weather lashing parts of South Australia.
Adelaide "may just get spared the worst of the weather" tonight but destructive winds are forecast to lash Kangaroo Island, Yorke Peninsula and South Australia's mid north.
Western Australia has responded to a request from South Australia for replacement transmission towers, after more than 20 were destroyed.