After a hot, dry couple of days, the Hunter is about to cop an absolute drenching.
The BOM is forecasting heavy rainfall to develop from Tuesday afternoon, which could lead to "localised flash flooding and rises in rivers and streams."
Coastal suburbs are likely to get most of the rain on Wednesday, especially around Port Stephens, with up to 100mm over 24 hours possible.
However inland parts of the Hunter can also expect decent falls.
The BOM predicts the rain is unlikely to clear until the weekend.
It's prompted a warning from the SES for residents to clean gutters, drains and downpipes, and park cars under cover away from stormwater drains.
Motorists are also being advised not to drive through floodwaters.