New South Wales is in the midst of a 'one-in-100-year' weather event, according to the MidCoast Council, as relentless rainfall forces residents in flood-hit areas to evacuate from their homes.
The Bureau of Meteorology expects Monday to bring the worst flooding event to the area northwest of Sydney since November 1961, nearly 50 years ago.
Floodwaters are expected to rise to major levels on Monday morning and inundate places such as Windsor, Pitt Town, North Richmond, Freemans Reach and Colo.
The Hawkesbury river is predicted to reach peaks of up to 15 metres and the State Emergency Service says homes and properties will be flooded, some up to roof height.
Flooding along the Hawkesbury and Nepean rivers comes after the Warragamba Dam spilled over, prompting some concern.
Parts of Penrith and other areas along the Nepean were ordered to evacuate on Sunday as NSW battles devastating floods after days of unabated rain.
BOM's Agata Imielska said the severity of rainfall in greater Sydney would ease on Monday but the mid-north coast would continue to be drenched and inland NSW would be pounded by rain.
Parts of Port Macquarie, Taree and nearby towns have also flooded, with the heavy rain expected to keep falling on NSW until Wednesday morning.
The federal government's natural disaster arrangements have been activated for 18 local government areas across NSW.
NSW's SES says it will work beyond Easter on the post-flood clean up effort.
The photos below show some of the devastating damage caused so far.