A slow-moving cold front will continue to cause heavy rain in southwestern Australia on Wednesday after some areas collected more than 50 mm of rain in less than six hours on Tuesday night, prompting warnings for flash flooding.

Cold fronts are not unusual in the southwest of Western Australia during winter. However, the front crossing on Tuesday and Wednesday this week is causing intense rainfall due to its slow movement over the region.

Slow-moving cold fronts allow rainfall to persist over a region for a prolonged period, which can significantly increase accumulated rainfall totals and boost the risk of flash flooding. When multiple showers or thunderstorms pass over one region repeatedly, meteorologists refer to this as ‘training’ because the showers or storms are travelling along a line that is stationary, similar to train carriages moving along a track.

The radar animation below shows showers training over the southwest of WA on Tuesday night and Wednesday morning.

A rain gauge at Ravenscliffe, located southeast of Busselton, registered 50.8 mm of rain in the five hours ending at 12:30 am on Wednesday. Busselton also picked up 20 mm in less than three hours late on Tuesday night.

The heavy rain on Tuesday night prompted the Bureau of Meteorology to issue a severe weather warning for flash flooding in parts of WA’s South West and Lower West districts. Persistent rain and thunderstorms will continue in these areas on Wednesday, possibly causing six-hourly rain rates of 30 to 60 mm.

While Perth was not included in the warning area early on Wednesday morning, rain will spread north across the city during the afternoon and may cause isolated heavy falls. Drier weather will return to the southwest of WA on Thursday as the rain spreads further north and east across the state.

Beyond the southwest, this weather system will continue to impact other parts of WA in the coming days.

A slow-moving upper-level low pressure system is expected to cause several days of rain and thunderstorms over the central and southern interior of WA between Thursday and Sunday, including the Goldfields, Central Wheat Belt, and Great Southern districts.

Image: Forecast accumulated rain during the 72 hours ending at 8 pm AWST on Friday, August 28, 2026. Source: Weatherzone.

The Bureau may issue further severe weather or severe thunderstorm warnings as this system continues to impact WA over the coming days.