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.
Perth hit a scorching 40.4 degrees Celsius on day one of a heatwave that is expected to last for at least five days.
After a wet start to the year, southeastern Australia is drying out, beginning its driest spell in about two months.
Around 20 cars became partially submerged after falling through a temporary car park established on Wisconsin's frozen Lake Geneva on Saturday local time.