Heavy rain and widespread storms over NSW have prompted hundreds of calls for help across Sydney and some regional areas as rivers rise to flood levels.

The NSW State Emergency Service responded to 460 incidents in the 24 hours to Tuesday morning, the majority in the metropolitan area.

But 75 occurred in north-eastern NSW, where there are flood warnings after major downpours.

SES personnel helped rescue people from three vehicles trapped in floodwaters, with all of those involved now safe.

Deluges were widespread across the state, including at Dorrigo, west of Coffs Harbour, which had 238 millimetres over 24 hours.

Numerous warnings were issued, including watch and act directions for rivers in the Coffs Harbour area.

The Orara River at Glenreagh, south of Grafton, neared a minor flood peak of 7.5m on Tuesday morning. Higher levels are possible with more rain forecast.

A minor flood warning was also issued for the Bellingen River, south of Coffs Harbour, after 160 millimetres of rain fell at nearby Thora in less than 12 hours.

Residents on the Bellinger River at Darkwood were told to prepare to become isolated by the rising water.

“You may be trapped without power, water, and other essential services and it may be too dangerous for NSW SES to rescue you,” the SES said.

Other waterways north of Port Macquarie and in north-western NSW were at advice level, with further rainfall potentially worsening conditions.

-AAP