The monsoon has officially arrived at Darwin, bringing cooling rain to northern Australia after persistent hot and humid conditions.
The initial monsoon onset at Darwin Airport, defined by the seasonal reversal of winds over the tropics, occurred on Tuesday 23 December 2025.
Active monsoon periods generally result in wetter weather over much of northern Australia.
The monsoon is associated with cloudy conditions, lengthy periods of heavy rain, occasional thunderstorms and fresh to strong squally winds. This often causes flooding in affected areas.
Ask the Bureau: What is the monsoon?
Senior Meteorologist Jonathan How explains how the Australian monsoon delivers most of the annual rainfall across our tropical north.
A monsoon is a seasonal wind change bringing widespread long lasting rainfall across the world's tropical areas, including northern Australia during the wet season. In the buildup to the wet season, summertime heating warms up the land faster than the surrounding oceans, creating an area of low pressure. This helps to draw the monsoon trough south over the Australian continent with dry southeasterly trade winds shifting to moist north-westerly winds. When this wind change arrives, the tropics are affected by monsoonal conditions. During an active monsoon, the sky is filled with dark clouds bringing widespread rain and thunderstorms. These wet conditions can last for a few days or even a week or more. An active monsoon period can be followed by an inactive or break monsoon period. This is when the weather returns to pre-monsoonal or buildup conditions. Northern Australia typically sees about three monsoon bursts each wet season. Monsoonal rains deliver the majority of the annual rainfall across the tropical north. Although it can cause flooding and cut off roads, it's also vital for life across the tropical north.
Why is the monsoon onset measured at Darwin?
The Australian monsoon onset is measured at Darwin to provide a consistent location for the reversal of winds that defines the monsoon. This allows for a long-term and standardised record of the event's timing, providing a long history of reliable wind data that meteorologists can use to compare seasonal variations over many years. Monsoon-like conditions can happen across other parts of northern Australia without reaching the official wind criteria in Darwin.
Communities across northern Australia should always be prepared during the wet season, which is the peak time for heavy rainfall, flooding, thunderstorms and tropical lows and cyclones.
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