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.
Temperatures will remain above 40 degrees Celsius in parts of central and southern Queensland until at least Wednesday next week, the Bureau of Meterology (BOM) warns.
Hot weather can take a serious toll on our health.
The sort of temperatures that see roads melt and cold taps flowing with boiling water are set to scorch Sydney and northern New South Wales over the next few days with the weather bureau officially forecasting a rare "extreme heatwave".