Rainfall in El Niño years

An El Niño event often results in less rainfall than average over much of eastern Australia.

The 14 strongest El Niño events which had the 'classic' autumn to autumn pattern of evolution and decay, started in 1905, 1914, 1940, 1941, 1946, 1965, 1972, 1977,1982, 1991, 1994, 1997, 2002 and 2015.

Winter–spring

The map below shows below average (deciles 2 or 3, indicated by the red shading) for the six-month winter–spring period, across much of eastern Australia. Regions specifically affected include the northeastern half of Tasmania, almost all of Victoria, almost all of New South Wales (excluding coastal districts), eastern and coastal parts of South Australia, and much of Queensland. Small coastal areas in southern Western Australia are affected, as is the north of the Northern Territory.

Winter–Spring mean rainfall deciles across Australia El Niño years.
Figure 1: Australian Winter–Spring mean rainfall deciles for 14 El Niño events.

It should be remembered that the winter–spring period covers a lot of the dry season for northern Australia. In the dry season, zero monthly rainfall totals are quite common in some northern and central parts even in ordinary years, so it is not surprising that there is little or no consistent El Niño effect for this time of year across central and southern parts of the Northern Territory and adjacent parts of Western Australia. In no parts of the country is there a consistent tendency towards above average (decile 8 or higher) rainfall in El Niño years.

It should not be expected that winter–spring rainfall in any given El Niño year will follow the pattern of Figure 1, nor should it be expected that 'above average' rainfalls will not occur during an El Niño year.

Winter–spring rainfall: 1905 1914 1940 1941 1946 1965 1972 1977 1982 1991 1994 1997 2002 2015

Winter spring temperature

El Niño years tend to see warmer-than-average temperatures across most of southern Australia, particularly in the spring and summer months. Although maximum temperatures are generally warmer than average, decreased cloud cover often leads to cooler-than-average night-time temperatures during winter–spring and a longer frost season.

El Niño June–November maximum temperature deciles composite map El Niño June–November minimum temperature deciles composite map

Summer rainfall

Generally, El Niño's impact on Australian rainfall diminishes from November onwards, so that by summer (Figure 2), the El Niño-induced tendency towards drier than average conditions has almost entirely broken down across the east and south of the country. The most significant exceptions are the east of Cape York and northwest Tasmania, both of which have a moderate drier response. Scattered areas along the Queensland/New South Wales border show a weak tendency for wetter conditions. There is a somewhat stronger and more widespread tendency for wetter than average conditions over the southeast of Western Australia.

Summer mean rainfall deciles across Australia for twelve El Niño years.
Figure 2: Australian Summer mean rainfall deciles for 14 El Niño events.

It should not be expected that summer rainfall in any given El Niño event will follow the pattern of Figure 2. Furthermore, as the influence of El Niño often decreases during the season, it is possible for there to be a marked contrast between the rainfall patterns of early and late summer. That is, hot and dry conditions in the first part of the season can be replaced by milder, wetter weather in the second part.

Summer rainfall: 1905–06 1914–15 1940–41 1941–42 1946–47 1965–66 1972–73 1977–78 1982–83 1991–92 1994–95 1997–98 2002–03 2015–16

Summer temperature

El Niño summers tend to be warmer across south eastern Australia with hotter daily temperature extremes but fewer long warm spells. Further north, El Niño is associated with both an increase in individual extreme hot days and multi-day warm spells.

El Niño December–February maximum temperature deciles composite map El Niño December–February minimum temperature deciles composite map

About the maps

Both of the maps above are composites of 14 El Niño years. For each of these El Niño years, the deciles for the winter–spring and summer periods are calculated against all years from 1900 to 2019. These deciles are then averaged for each point in Australia, and the result mapped. Rainfall for El Niño years will not follow an identical pattern to the maps above. These maps show average patterns. In reality, each event will be slightly different and it is always possible for areas of above-average rainfall to still occur during an El Niño event.