Sydney has recorded its wettest August in 27 years, pushing the city’s climate into unprecedented territory. Data from Observatory Hill, which has been collected since 1858, shows that rainfall over the past six years has reached the highest levels on record. Since January 2020, Sydney has received more than 9,300 millimeters of rain, surpassing the previous record of 9,120 millimeters set between 1985 and 1990. With heavy rain expected to continue this week and more than four months remaining in 2025, the total is projected to rise significantly by the end of December.

The shift in Sydney's weather patterns began after a severe drought that lasted from 2017 to 2019. In early 2020, the city experienced flooding rains, marking the wettest February in three decades. This event initiated what would become Sydney's wettest year of the century, with an annual total of 1,552 millimeters, compared to the long-term average of 1,221 millimeters. The following year, 2021, also saw above-average rainfall at 1,290 millimeters. However, 2022 set a new record with 2,530 millimeters. Rainfall dipped below normal in 2023 due to El Niño, but rebounded to 1,641 millimeters in 2024, which would have been the wettest year since 1998 if not for 2022.

As of now, 2025 has continued this trend, with rainfall already exceeding the annual average despite it still being winter. Meteorologists are investigating the reasons behind this unprecedented rainfall and whether it signifies a new normal in a warming climate. Analysis from the National Oceanic and Atmospheric Administration indicates a significant change in wind patterns along the New South Wales coast. Since 2020, winds have been blowing stronger and more frequently from the east. In 2025, the average wind speed in Sydney has deviated from the east by 5 kilometers per hour, a notable change over time.

A major climate driver is emerging, suggesting a wet end to the year for Australia. The easterly winds, which are the primary source of moisture for Sydney, have contributed to the increased rainfall. This change in wind patterns is linked to climate change, specifically a shift in high-pressure zones over southern Australia. As these high-pressure systems move south, they reduce dry westerly winds and increase humid easterlies.

The key question remains whether the past six years of increased rainfall is a temporary anomaly or a permanent shift in Sydney's climate. While it is uncertain, other regions in southern Australia have shown clear rainfall trends over the past few decades, indicating that Sydney may have entered a wetter climate phase.

Late winter typically brings drier conditions to Sydney, but by late Monday, the Observatory Hill weather station had already recorded about three times the monthly average of 80 millimeters. Rain has fallen on 76 percent of days in the past three weeks, with forecasts predicting an additional 100 millimeters of rain by Friday. This could push the monthly total above 300 millimeters, making it the fourth wettest August in 167 years of recorded data.

The current rainfall is attributed to a high-pressure system to the south that is directing moist winds onto the coast. Additionally, a mass of polar air moving over southeastern Australia is expected to bring heavy rain and thunderstorms to northern New South Wales, prompting a flood watch for the Mid North Coast and North West Slopes.

Looking ahead, weather models suggest a return to drier westerly winds next week, which is more typical for August and should bring sunnier days. However, the long-range forecast for spring indicates a strong likelihood of above-average rainfall across eastern Australia.