| Impact |
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 2010 Australia’s third-wettest calendar year, wettest on record for the Murray-Darling Basin and Queensland- Australia’s wettest two-calendar year period (2010–2011)
- Southwest Australia’s driest year on record
|
|
 El Niño breaking down |
- Australia’s wettest 24-month period on record (April 2010–March 2012)
- Australia’s third-wettest 12-month period (April 2010–March 2011)
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 Wettest ‘dry’ season on record for northern and central Australia (May–October) |
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- Above-average monthly rainfall for most of Australia (July 2010–March 2011)
- Wettest second half of the year on record for Australia
|
 Floods and landslips in northeast Tasmania (10–11 August) |
- Wettest September on record for Australia
- Wettest spring on record for Australia, and all states except Tasmania and Victoria
- Major flooding in northern Victoria (early September)
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- Second-wettest October on record for Australia
- Floods in southeast Queensland (10–12 October) – Wivenhoe Dam spills for the first time since 2001
- Floods in Riverina and southwest slopes New South Wales (13–16 October)
- Record-high sea surface temperatures around the northern coasts of Australia (October–December)
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- Wet season second wettest on record for northern Australia, Queensland, and Western Australia (November 2010–April 2011)
- Australian monsoon arrives earlier and is stronger than normal
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- Wettest December on record for Australia and Victoria
- Wettest summer on record for Victoria, second-wettest for Western Australia and Australia as a whole
- Widespread flooding on inland rivers , especially in New South Wales (early December)
- Severe floods in the Gascoyne associated with a tropical depression (16–18 December)
- Severe floods in southern and central Queensland (mid-December–January)
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- 2011 Australia’s second-wettest calendar year, wettest on record for Western Australia
- Wettest January on record for Queensland and Victoria
- Flooding in western and central Victoria and northern Tasmania (12–15 January)
- Flooding in northeastern and western New South Wales and southeast Queensland, notably in Brisbane River catchment and severe flash floods in Toowoomba/Lockyer Valley.
- Tropical cyclone Bianca brings rain and strong winds to the Kimberley and Pilbara (25–30 January)
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 Second-wettest February on record for Australia- Tropical cyclone Yasi strongest to hit Queensland coast since at least 1918 (3 February)
- Severe thunderstorms associated with ex-tropical cyclone Anthony cause flash flooding in Victoria (4 February)
- Tropical cyclone Carlos inundates Darwin (15–17 February)
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- Wettest March on record for northern Australia
- Monsoonal burst causes flooding in eastern Kimberley (week ending 14 March)
- Prolonged flooding across western Queensland
- Flooding in northeastern Tasmania, southeast New South Wales, and Gippsland (20–24 March)
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- Flash flooding and river flooding in eastern Tasmania (10–13 April)
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 Increased vegetation following high rainfall in 2010 and 2011 fuels widespread grassfires in central Australia (August–November) |
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- Rainfall above average for most of mainland Australia (October 2011–March 2012)
- Australia’s record highest October rainfall total: 1494 mm at Bellenden Ker
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- Second-wettest November and spring on record for Western Australia
- Extensive flooding through northeastern New South Wales west of the Great Divide (late November)
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- Sea surface temperatures around northern Australia above average (December 2011–February 2012)
- Tropical cyclone Grant brings very heavy rain to the Top End (25–26 December)
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- Extended flooding in northern New South Wales (late January)
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- Severe flooding in inland southern Queensland and northeast New South Wales (early February–March)
- Torrential rain in central and northeast Victoria cause flash flooding (late February)
- Flooding in southern New South Wales and northern Victoria (record seven-day falls, 27 February–4 March)
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- Second-wettest March on record for New South Wales
- Heavy rain exacerbates flooding from northern Victoria through southeast and western Queensland
- Tropical cyclone Lua strongest to cross the Western Australian coast since Laurence in 2009 (17 March)
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- Australia’s rainfall 43 per cent below average for April
- Monthly rainfall across the Murray-Darling Basin 63 per cent below average
|
| Date |
Dec-09 |
Jan-10 |
Feb-10 |
Mar-10 |
Apr-10 |
May-10 |
Jun-10 |
Jul-10 |
Aug-10 |
Sep-10 |
Oct-10 |
Nov-10 |
Dec-10 |
Jan-11 |
Feb-11 |
Mar-11 |
Apr-11 |
May-11 |
Jun-11 |
Jul-11 |
Aug-11 |
Sep-11 |
Oct-11 |
Nov-11 |
Dec-11 |
Jan-12 |
Feb-12 |
March-12 |
April 2012 |
| Indicator |
 2009–10 El Niño reaches its peak around late December |
|
|
 Pacific Ocean cools rapidly during autumn- Positive SAM (March 2010–February 2011 – record high values June, July, and November, second highest for August and October)
|
 ENSO indicators neutral by late April- Climate models suggest increased chance of La Niña
|
 First signs of La Niña apparent |
 Sea surface temperatures approach La Niña thresholds |
- Bureau announces La Niña about to become established.
- Climate models predict La Niñalikely to persist through the remainder of 2010
- First indication of falling IOD index
|
- Negative IOD event (late August–late November)
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- Monthly SOI second highest on record (+25.0), also the highest monthly value for any month since November 1973
- IOD strongly negative (September–November)
|
 Monthly SOI equal highest on record (+18.3) for October- Bureau seasonal outlooks indicate very high probability of above-average spring–summer rainfall for parts of Queensland and New South Wales
- Climate models predict La Niña conditions into first quarter 2011
|
- Negative IOD event decays
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- Monthly SOI highest on record (+27.1) for December
|
- Monthly SOI third highest on record (+19.9) for January
- 2010–11 La Niña reaches its peak
- Unusually warm sea surface temperatures in the western Pacific Ocean
|
- Monthly SOI highest on record (+22.3) for February
- Climate models predict La Niña to decline to neutral by winter
|
 Monthly SOI highest on record (+21.4) for March- Oceanic ENSO indicators decline but atmospheric indicators continue to indicate strong La Niña conditions (late March)
- Climate models forecast neutral ENSO conditions by winter
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- Monthly SOI second highest on record (+25.1) for April
|
- Sharp drop in SOI
- 2010–11 La Niña ends
- Pacific Ocean begins cooling
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- Model outlooks indicate re-emergence of La Niña likely
- Brief, weakly positive IOD event during spring
|
- 2011–12 La Niña declared mid-October, forecast not to be as strong as the 2010–11 La Niña
|
|
 Monthly SOI equal second highest on record (+23.0) for December- 2011–12 La Niña reaches its peak
|
|
 Most oceanic ENSO indicators return to neutral |
- 2011–12 La Niña ends late-March
|
- Some climate models indicate that an El Niño may emerge later in 2012
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