Indian Ocean Dipole in Australia infographic. What is the Indian Ocean Dipole? The Indian Ocean Dipole is the difference in ocean temperatures between the west and east tropical Indian Ocean, that can shift moisture towards or away from Australia. When do they occur? The Indian Ocean Dipole can impact from May to December and last for two to seven months. The Indian Ocean Dipole doesn't form during summer due to the Australian monsoon. Map showing the typical below average winter to spring rainfall over central and eastern Australia during a positive Indian Ocean Dipole event. Typical impacts in a positive Indian Ocean Dipole phase include: less rainfall over central and southern Australia, warmer days in the west and south, warmer nights in the southwest, cooler nights in the north, shorter snow season, lower snow depths, and increased fire risk in the southeast. A positive Indian Ocean Dipole phase is more likely to coincide with El Niņo. In 1982 southeast Australia had its driest year on record when a positive Indian Ocean Dipole coincided with El Niņo. Diagram showing the typical ocean and atmosphere conditions during a positive Indian Ocean Dipole. Above average sea surface temperatures and cloudiness in the western tropical Indian Ocean, and below average sea surface temperatures and cloudiness in the eastern tropical Indian Ocean. Map showing the typical above average winter to spring rainfall over southern and eastern Australia during a negative Indian Ocean Dipole. Typical impacts in a negative Indian Ocean Dipole phase include more rainfall over eastern and southern Australia, cooler days in the south, warmer nights in the north, increased chance of flooding, more northwest cloud bands. A negative Indian Ocean Dipole phase is more likely to coincide with La Niņa. In 1974 Australia had its wettest year on record when a negative Indian Ocean Dipole coincided with La Niņa. Diagram showing the typical ocean and atmosphere conditions during a negative Indian Ocean Dipole. Below average sea surface temperatures and cloudiness in the western tropical Indian Ocean, and above average sea surface temperatures and cloudiness in the eastern tropical Indian Ocean.