Sydney: Climate and water
- Total annual rainfall during the 2021-22 year was the region's third wettest year on record following record-breaking rainfall during March 2022.
- A weak negative Indian Ocean Dipole and the development and strenghtening of La Nina over the summer months produced above-average rainfall from November to May.
- Two East Coast Lows resulted in the wettest March on record, causing significant flooding to the region.
- Record-breaking rainfall resulted in some streamflows being almost five times above the annual average.
For further information on the region's climate and water conditions during the 2021-22 year scroll down this page or click on the links below:
About the region
- The Sydney region has a temperate climate with warm summers (December–February) and mild winters (June–August).
- Rainfall occurs throughout the year with most rainfall occurring during the summer and autumn months. Higher streamflows typically occur during these months.
Climate conditions
Rainfall
Figure C1 Annual and monthly rainfall deciles for the Sydney region during the 2021-22 year
- Total area-averaged rainfall for the 2021-22 year was 1,469 mm; well above the mean value of 888 mm.
- A weak negative Indian Ocean Dipole and developing La Nina resulted in the region having its third wettest year on record, only surpassed by 1955-56 and 1949-50.
- Rainfall during the first four months (July to October 2021) were below the long-term averages, except for August.
- The development of La Nina resulted in rainfall being more than twice the long-term average for November, with some areas experiencing their wettest November on record.
- During summer, the strengthening La Nina resulted in above-average rainfall for all summer months.
- Following above average rainfall during summer, the development of two East Coast Lows produced record-breaking rainfall across the region during March. Not only was it the wettest March on record, but also the wettest month (of any month) on record. In addition to the record-breaking rainfall during March, it was also the wettest autumn on record, and the wettest October to March period on record.
- By June, oceanic indicators of ENSO returned to neutral, and despite some atmospheric indicators showing a La Nina-like signal, rainfall in June was predominantly very much below average.
Figure C2 Total monthly rainfall for the Sydney region during the 2021-22 year compared with the average and percentiles for the region
- Rainfall in November 2021 and March 2022 were well-above the 90th percentile, while December 2021 was just above the 90th percentile.
- March 2022 was the region's wettest March on record, with rainfall being more than four times the monthly average. It was also the region's wettest month (of all months) on record.
- June 2022 was the only month to record rainfall below the 10th percentile.
Actual evapotranspiration
Figure C3 Annual and monthly actual evapotranspiration deciles for the Sydney region during the 2021-22 year
- Total area-averaged actual evapotranspiration for the 2021-22 year was predominantly very much above average across the region, with southern areas experiencing their highest evapotranspiration on record.
- During the first five months (July to November 2021), evapotranspiration was predominantly average to above average, with smaller pockets of below-average evapotranspiration appearing each month, except for October.
- Following the development of La Nina in November, evapotranspiration was generally above average to very much above average across the summer months due to increased water availability following high rainfall occurring from November onwards.
- Evapotranspiration continued to be above average to very much above average for the remainder of the 2021-22 year; a result of the impacts from La Nina.
- By June, La Nina had weakened, but evapotranspiration was still average to above average across most of the region.
Soil moisture
Figure C4 Annual and monthly soil moisture deciles for the Sydney region during the 2021-22 year
- Soil moisture in the root zone (0–1 m depth) for the 2021-22 year was at least above average for the entire region following the third wettest year on record.
- During the first four months (July to October 2021), soil moisture was predominantly average, with some areas of below-average soil moisture.
- Between November 2021 and May 2022, soil moisture was generally above average to very much above average after the region experienced record-breaking rainfall from November to March because of a La Nina event.
- Despite below-average rainfall in June 2022, soil moisture was average to above average due to the very wet antecedent conditions during the year.
Streamflow responses
Figure C5 Key flow gauging stations along the main rivers within
the Sydney region
- The Hawkesbury–Nepean and Shoalhaven river systems are two primary river systems within the Sydney region.
- Streamflow along these rivers upstream of the above gauging stations is unregulated and not influenced by diversions for consumptive use.
Figure C6 Total monthly flow for major rivers in the Sydney region during the 2021-22 year compared with the average and percentiles
- Streamflows during the first four months were predominantly average, however, following a wet November, streamflows for both sites increased to register flow volumes well-above the 90th percentile.
- From November 2021 to June 2022, streamflows remained well-above the 90th percentile for most months, due to the development of a La Nina during spring and summer, resulting in the region's third wettest year on record and wettest October to March period on record.
- In March 2022, streamflows were the highest on record for March, following record-breaking rainfall, mainly caused by two separate East Coast Lows, that broke multiple rainfall records and produced widespread flooding across the region.
- More information on the extreme rainfall and flooding across the region can be found in the Bureau's Special Climate Statement 76.