Major flood warning for Nepean River

The SES is warning of major floods in the upper reaches of the Nepean River with further heavy rain expected to add to the 374mm of rain already fallen.

Major floods are predicted around the Nepean River after 374mm of rain fell in its catchment. (AAP)

Major floods are predicted around the Nepean River after 374mm of rain fell in its catchment area during the weekend's wild weather.

Further heavy rain - about 100mm - is predicted to hit the Nepean and Wollondilly regions on Sunday evening, which is expected to cause major flooding at Menangle and moderate flooding downstream, the SES says.

The Nepean River was recorded at a height of 3.41 metres at the Menangle weir on Sunday afternoon and the waters are due to continue rising.