Sydney is in for a wet week, with a low pressure system to head across NSW today.
This will result in a large amount of rainfall in the Sydney and Illawarra tomorrow.
The Bureau of Meteorology has issued a severe weather warning, with 'intense rain and vigorous winds' on the way.
"Heavy rain which may lead to flash flooding is likely for some parts of the Illawarra, Sydney Metropolitan and Blue Mountains during Wednesday," a BoM said.
"The most intense rainfall is likely to be during Wednesday morning and afternoon."
In fact, the amount of rainfall is set to just about double the amount we've already seen this month, with the heaviest coming late Wednesday morning.