Parts of New South Wales have been hit by near-record rainfall as a weather system moving across the state is giving Sydney a wet end to the month.
It comes as the SES has warned large parts of the state, including Sydney, to prepare for the risk of flash floods.
Authorities warn rainfall will shift from inland areas to parts of the NSW Mid North Coast, and Hunter Valley regions, and could extend into Greater Sydney and the Illawarra.
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"Daily rainfall totals of 20-40mm are likely, with locally heavy falls of 70-80mm possible with slow-moving thunderstorms," the SES warned in a statement.
Dubbo in the state's Central West had nearly 60mm of rain in just 24 hours to 9am yesterday, with the 59.4mm recorded becoming the equal second-wettest day in May since records began in 1870.
The reason for the wet weather is because a low-pressure system and slow-moving troughs are moving across the state.
"Pools of cold upper-level air cause the atmosphere to become unstable, paving the way for wet and stormy weather," Weatherzone's Anthony Sharwood said.
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The rain is set to get worse as the week wears on, with Sydney set to be in the firing line.
Sydney received around 15mm of rain since 9 am yesterday, and could see around 5mm today, with the city draped in fog this morning.
However, it will cop a drenching to end the week, with 80mm of rain potentially falling on Thursday and Friday.
According to Weatherzone, Sydney will get a slight reprieve over the weekend as rainfall eases, but it could ramp up by early next week.
