A rare burst of tropical moisture is poised to drench Adelaide while unusually warm ocean waters keep Sydney feeling more like autumn than the brink of winter.
Large parts of South Australia are bracing for widespread rain as a slow-moving inland trough draws humid air from the tropics.
Rain is forecast to build from Friday and persist on and off through the weekend in the Adelaide region, with storms possible on Saturday.
The wet weather is expected to interrupt outdoor plans but will be welcomed after a comparatively dry start to the year for the city and surrounding districts.
Weatherzone meteorologist Jess Miskelly said the system’s unusual movement could allow rainfall to linger longer than typical winter fronts.
“It’s also a slow-moving system, with the trough and front sliding southeast rather than pushing east due to the blocking high over the Tasman,” Ms Miskelly said.
“This means the system will be in the vicinity longer, hence able to cause more rain.”
Adelaide recorded a completely dry January this year, with even Mount Lofty receiving just 1.8mm during the month. Since then, rainfall has hovered near average without any major soaking events.
That could soon change, with forecasts suggesting between 15mm and 40mm may fall between Friday and Tuesday, potentially marking the city’s wettest stretch of 2026 so far.
The incoming rain will arrive from the north and northeast, a direction rarely linked with significant Adelaide rainfall, and could help replenish water storages and boost inflows into Kati Thanda-Lake Eyre, which already holds extensive water up to 2.2m deep.
Meanwhile on the east coast, the Tasman Sea is reshaping weather patterns in NSW.
Unusually warm ocean temperatures have developed in large pools known as eddies, driven south by the East Australian Current.
These waters are sitting about 2C to 4C above the seasonal average and are among the warmest recorded for this time of year.
The warmth has pushed Sydney’s daytime temperatures several degrees above normal, with the city recording its warmest start to May in eight years.
Onshore winds are also carrying moisture inland, bringing showers along the coast and ranges while keeping beach swims unusually appealing for late autumn.
Relatively warm and showery conditions are forecast to continue for the rest of the week, with Sydney expected to reach daytime highs of 22 to 24C, several degrees above the May average of 19.6C.