Multiple flood evacuation orders have been issued instructing people in western parts of Sydney to leave their homes immediately amid growing threats of dangerous flooding.
The NSW State Emergency Services (SES) told people in the northern end of Mulgoa, in Penrith, to evacuate before 9pm on Sunday along Martin Street between Mulgoa Creek, and the Nepean River area to evacuate using the Mulgoa Road Evacuation Route.
People in the western part of Jamisontown, also in Penrith, have been told to evacuate before 9pm on Sunday using the Great Western Highway Evacuation Route as well.
Earlier on Sunday, residents in western parts of Penrith were told they needed to leave before 4.30pm.
The Nepean River at Penrith could rise as high as 10 metres by 9pm, while the river at Richmond and Windsor could peak about 16 metres on Monday.
NSW SES said safety could not be guaranteed for people who missed the 9pm evacuation cut-off time.
"It was our precaution to get it done by that time and it's not guaranteed that they will be able to get out after that time," media spokesperson Andrew McCullough told Yahoo News Australia.
"We issued the evacuation order and generally, that's the time people will be able to get out safely."
About 1000 people were sent a text message from NSW SES alerting them to the 4.30pm and 9pm evacuation order.
"People need to heed the warnings and leave within that time to be safe," Mr McCullough said.
Of the people subject to the 4.30pm evacuation order, announced to Twitter by NSW SES about 4pm, he said some people had left but he wasn't sure how many had been able to flee.
People in the area would have received text messages and calls alerting them to the imminent danger, Mr McCullough said.
He added there had been no reported issues with the service's website despite some claiming they had issues accessing evacuation information relevant to them.
Penrith floods are 'one-in-60-year' event
The Bureau of Meteorology's Justin Robinson said river levels in Penrith would be comparable to those seen 60 years ago in the 1961 floods.
"We are very concerned about the flooding in the Hawkesbury-Nepean Valley," he told reporters on Sunday.
"It is one of the biggest floods we are likely to see for a very long time... flood waters at Penrith are expected to then move downstream and impact those communities at North Richmond, Windsor, Sackville."
Several roads blocked amid evacuations
Residents in evacuation areas will need to plan their exit strategy carefully to avoid running into trouble on one of several roads blocked due to flooding, debris and landslide threats.
Current road closures:
Jenolan Caves Road between Great Western Highway and Edith Road.
Great Western Highway at Evans Lookout Road in Blackheath.
Illawarra Highway between Mount Murray Road and Escarpment Drive/Yellow Rock Road at Macquarie Pass.
Oxley Highway between Mount Seaview Road and Brackendale Road, impacting traffic from Mount Seaview to Walcha.
Waterfall Way between Maynards Plains Road and Horseshoe Road from Dorrigo Mountain to Thora.
Pacific Highway between George Gibson Drive and Manning River Drive/Old Bar Road, stretching from Coopernook to Glenthorne.
Oxley Highway between Henry Street and Billabong Drive, from Long Flat to Sancrox.
Bells Line of Road (Hawkesbury River bridge) between Pitt Lane and Old Kurrajong Road in Richmond. The bridge is closed in both directions.
City receives huge downpour
Elsewhere, the Sydney CBD was drenched by 110mm of rain over the same 24-hour period, while 120mm hit Hornsby and 168mm reached Katoomba.
The bureau's Agata Imielska said the severity of rain hitting Greater Sydney would ease from Sunday night, but the Mid North Coast would continue to be drenched and inland NSW would be deluged from Monday.
Ms Imielska said the NSW northwest slopes and plains would receive four times more rain in two days than the entire March monthly average.
The NSW south coast would also experience heavy rain from Tuesday.
SES Deputy Commissioner Daniel Austin told the ABC the service was dealing with downed trees, power outages, clearing of debris and damage to houses.
More evacuations possible
The SES has responded to almost 7000 calls for help since Thursday.
Premier Gladys Berejiklian on Sunday said the Hawkesbury-Nepean Valley flood could prompt an additional 4000 evacuations by the end of Sunday.
This includes residents downstream of the Lower Mooney Dam on the Central Coast, which the SES said on Sunday was beginning to spill over.
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