Sydney has experienced an unprecedented deluge in August 2025, recording its wettest August in 27 years. As of August 21, rainfall totals have surpassed 345 millimeters, a stark contrast to the typical monthly average of 79.9 millimeters. This persistent downpour has led to significant flooding across New South Wales and Queensland, with severe flood warnings issued for the NSW mid-north coast and major flooding impacting areas like Tamworth, Armidale, and Moree.
The intensity of the rainfall is highlighted by the 82.4 millimeters recorded in Sydney on August 20 alone, marking the wettest August day since 2007. This extreme weather event is attributed to a stationary high-pressure system situated over the Tasman Sea, which has been directing a consistent flow of moist air towards the coast. This meteorological setup has created a prolonged period of wet conditions, with forecasts indicating that the rain could continue to affect the region.
This event is part of a broader pattern of increased rainfall in Sydney. The city has already recorded its wettest start to August in decades, with totals more than double the monthly average by August 11. Furthermore, Sydney's Observatory Hill has registered over 9,300 mm of rain between January 2020 and August 2025, the highest six-year total since records began in 1858. The year 2022 alone saw an extraordinary 2,530 mm, setting a new annual record.
The New South Wales State Emergency Service (SES) has been actively responding to the crisis, handling hundreds of incidents, including critical flood rescues. The persistent wet weather has saturated the ground, exacerbating the risk of flash flooding and riverine flooding. The Bureau of Meteorology has noted that such stationary high-pressure systems can trap moist air, leading to prolonged periods of precipitation. This pattern, combined with unusually warm sea surface temperatures off the NSW coast, has fueled these consecutive heavy rainfall events.
The impact extends beyond Sydney, with significant rainfall totals recorded across NSW, including areas west of the Great Dividing Range, indicating the widespread nature of this weather system. The situation underscores the interconnectedness of atmospheric conditions and their profound effect on regional weather patterns, presenting both challenges and opportunities for adaptation and resilience.