The town of Hay has already been smashed with 23.6 millimetres of rain falling in just 30 minutes on Friday morning at the local airport.

On Friday morning the Bureau of Meteorology warned severe thunderstorms were developing along a trough moving through western and central NSW.

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The bureau said these storms were likely to produce heavy rainfall that may lead to flash flooding in the warning area over the next several hours.

The severe thunderstorms were expected to affect the Riverina towns of Griffith, Hay, Narrandera, Lockhart, Hillston and Darlington Point.

Despite the cancellation, heavy rains are still expected for parts of the region through Friday.

The State Emergency Service advises people to clear of creeks and storm drains, not walk, ride bikes or drive through flood water.

If trapped by flash flooding, residents and motorists are advised to seek refuge in the highest available place and ring 000 if in need of rescue.

The SES are also warning people that run-off from rainfall in fire affected areas may behave differently and be more rapid and may also contain debris such as ash, soil, trees and rocks.

After bushfires, heavy rain and the loss of foliage can make the ground soft and heavy, leading to a greater chance of landslides.

People are reminded to unplug computers and appliances and avoid using the phone during the storm.

The SES ask people to stay indoors away from windows, and keep children and pets indoors as well.

They also ask that people stay vigilant and monitor conditions. Note that the landscape may have changed following bushfires.

For emergency help in floods and storms, ring the SES (NSW and ACT) on 132 500.

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