Sea surface temperatures remained close to average monthly levels throughout the Great Barrier Reef during December 2011 and January 2012.  During February and March, temperatures rose 0.5 to 2.5°Celsius above average monthly levels. The exception was the upper reaches of the Far Northern region which recorded average or below average temperatures until the beginning of March, when this area too began to warm above average. Cloud cover during the later half of March prevented good temperature readings. Sea surface temperature data from April indicates that the above average monthly temperature  pattern continued during this period.

In the regions from Port Douglas to the Whitsundays, and offshore areas around the Pompeys and Swains Reefs, accumulated heat stress patterns measured by degree heating days (DHDs) exceeded the level (~100) known to be stressful to corals.  Around some inshore islands in the central sector, DHDs reached 120 – 140.  Towards the end of April, temperatures began to decrease back to average or below average levels in the southern and inshore central regions of the Marine Park (ReefTemp).

The observed conditions largely reflected the forecasts from the Bureau of Meteorology which indicated that Summer 2011/2012 would be dominated by moderate La Niña conditions which would weaken into a neutral state towards the beginning of April 2012. (Predictive Ocean Atmospheric Model for Australia)

No tropical cyclones crossed the Great Barrier Reef Marine Park during summer 2011/12.

December 2011 - average to above average rainfall throughout much of the Great Barrier Reef catchment, with the exception of the coastal areas of the Burdekin and Mackay regions.

January and February 2012 – the Burdekin River and the Fitzroy River upper catchments received above average rainfall resulting in major freshwater flows.  Other regions received variable rainfall, fluctuating above and below average levels.

March 2012 - above average rainfall throughout the majority of the Great Barrier Reef catchment, achieving the 7th wettest March on record (BoM).

Over much of the eastern half of Australia, the chances of receiving above median rainfall for autumn (March to May) were above 60 per cent (BoM).

The Burdekin and Fitzroy Rivers experienced major flows in early 2012, although not at the same extreme volumes observed during the 2010/2011 wet season. Visible plumes discharged from the Burdekin River from early January to March 2012.  Flows commenced out of the Fitzroy in February and continuing through March. Several other rivers had visible plumes to varying distances (up to 10-20 kilometres) during February and March. Smaller plumes (5-10 kilometres seaward) could be seen at times from many of the rivers between Cairns and Mackay (NASA). Flood warnings were issued for coastal and adjacent inland catchments from Cairns to Yeppoon for March (BoM).