Residents in Inverell and Glen Innes were deluged overnight as thunderstorms brought flash floods to the state's north-east.

Between midnight and 9am, 84mm of rain fell in Inverell while nearby Glen Innes recorded 70mm over the same period, the Bureau of Meteorology's senior forecaster Elly Spark said.

It was the heaviest daily November rainfall in 42 years for Inverell and in seven years for Glen Innes, weather service Weatherzone said.

The State Emergency Service of NSW said it received only a handful of calls from the area overnight and this morning, mostly about leaking roofs and submerged bridges.

"But there are some severe thunderstorms expected to develop in that part of the world again this afternoon, so we'll keep an eye on things," an SES spokesman said.

Weatherzone meteorologist Matt Pearce said: "This morning's storms were triggered by very moist air across northern NSW ahead of a trough of low pressure.

"The storms kept forming over the same locations, allowing rainfall totals to build up rapidly.

"Typically, the most severe storms develop during the afternoon and evening at this time of year. It is quite unusual to record such heavy rainfall during the early hours of the morning."