Sydney has experienced its wettest start to August in nearly three decades, with more than double the monthly average rainfall recorded in the first 11 days. According to Weatherzone, 194mm of rain fell by August 11, surpassing the monthly average of around 96mm and marking the wettest start to the month since 1998.
The heavy rain, driven by moist onshore winds, caused disruption across the city. The Byron Writers' Festival was cancelled, while 90,000 runners in the Sydney City2Surf event persevered through slippery conditions. Much of the NSW coastline, from the Illawarra to the Hunter and mid-north coast, has already reached or exceeded the monthly average, said Jonathan How, senior meteorologist at the Bureau of Meteorology.
Abnormally high sea surface temperatures off the coast have contributed to the wet conditions by boosting moisture content in clouds, How explained. A persistent high-pressure system over New Zealand has also pushed rain and moisture onto the coast. The wet start to August follows a wetter-than-usual July, with several locations recording their highest July rainfall on record.
University of Melbourne associate professor Andrew King noted that the NSW east coast is generally wet, but this year has been rainier than usual, particularly from the mid-north coast upwards. Several places recorded their wettest May on record after a low-pressure trough developed off the coast on 18 May and lingered for days. King highlighted that various systems, including thunderstorms, fronts, and east coast lows, can bring heavy rainfall to the region.
Despite the wet conditions in the east, August has been very dry inland, with many areas receiving little to no rain. The Bureau's long-range forecast for September to November anticipates above-average rainfall for the eastern two-thirds of Australia, with an increased chance of unusually high rainfall for parts of eastern Queensland, NSW, south-east South Australia, and northern Victoria. However, projections for NSW remain uncertain due to global heating, King said.
In the short term, Sydneysiders can expect some drier days ahead, with Friday likely to be the best day of the week. 'The good news is that the heaviest of the rain is now behind us,' How said.
