Level of annual rainfall

IBISWorld forecasts the level of annual rainfall to decrease by 3.5% in 2025-26, to 497.4 millimetres. At the time of writing only one month of rainfall data is available for the current year. As weather patterns are very difficult to predict, estimated rainfall levels in the current year are set to the long-term average.

Rainfall exhibits high volatility, with much of this coming from two global weather phenomena, La Niña and El Niño. El Niño is a weather phase that leads to above-average sea temperatures in the Pacific Ocean, creating warmer temperatures and reduced rainfall in Australia. La Niña is a weather phase that causes below-average sea temperatures in the Pacific Ocean, leading to wetter climate conditions in Australia. A La Niña weather phase often follows an El Niño weather phase. According to the BOM, above average rainfall for much of the eastern half of Australia is likely between September and November 2025. However, below average rainfall is likely for parts of Western Australia.

The BOM reported a La Niña event in September 2020, with a substantial shift toward cooler and wetter conditions occurring during the preceding months. These conditions contributed to above-average rainfall in 2020-21, with rainfall surging 48.1% over the previous year. Relatively high levels of annual rainfall persisted as La Niña weather events continued to influence the level of rainfall in Australia to near-record levels. November 2021 was the wettest November on record, while October 2022 was the second wettest October on record. However, many parts of Australia have experienced drier conditions over the past three years. September 2023 was the driest September on record and October 2023 was the fourth driest October on record. In addition, rainfall levels in January and June 2025 reached their lowest levels in five and six years respectively. Overall, IBISWorld forecasts the level of annual rainfall to fall at a compound annual rate of 0.6% over the five years through 2025-26.