Thick cloud over the coast and ranges of NSW in a trough and humid northeasterlies are producing widespread rain, with most areas between Taree and the Queensland border receiving at least 200mm since Friday.

Minor flooding on the Far North Coast has already closed back roads and schools.

Forecasts are for the rain to ease later today, which would avert major flooding in the northern parts.

According to FarmOnline Weather, in the 24 hours to 9am today, Byron Bay and Ballina picked up 124mm, their highest June daily rainfall in four years.

Nambucca Heads received 120mm in the same time period, making it their wettest day in four months. Alstonville recorded 118mm, their wettest day in three months.

Minor Flood Warnings are in force for the Bellinger, Nambucca and Orara Rivers.

Minor flooding is being reported from Thora in the headwaters of the Bellinger River.

"A very strong high pressure system in the southern Tasman Sea is directing moist easterly winds across northeast New South Wales," meteorologist Matt Pearce said.

"A trough of low pressure over the region is tapping into this moisture to trigger heavy falls of rain.

"Heavy showers will continue across the region through until tonight when the trough will move offshore.

"Partly cloudy skies tomorrow, with just a few, much lighter, showers will allow the floodwaters to recede quickly."

The rain cleared from Sydney early this morning, after dropping 44mm across the city during the last two days.

"Upper level atmospheric patterns are still favourable for more of these brief heavy rain events along the New South Wales coast over the next month or so.

"However, as we head further into winter and then spring, the potential for rain will drop off markedly with the likely development of an El Nino," Pearce said.