NSW hit by damaging winds and warm weather

NSW has been hit by damaging winds with gusts of more than 80km/h recorded in Sydney where two walls collapsed on separate building sites killing one man and critically injuring another.

The strong winds and unusually warm temperatures also led the Rural Fire Service to issue early alerts for two bushfires burning out of control at Moparrabah near the mid north coast.

As well, power lines were cut to 2900 homes and businesses across Sydney and the Central Coast.

The Bureau of Meteorology issued a severe weather warning for NSW on Wednesday with wind gusts of 83 km/h recorded in Sydney and gusts of up 100km/h hitting Mount Boyce in the Snowy Mountains.

Meteorologist Rose Barr says the wind and warm winter weather is due to air being squeezed between a high pressure system over the northern Tasman Sea and a strong low pressure system south of Victoria.

Sydney's average minimum temperature on Tuesday was 20C while inland temperatures stayed in the mid-teens across the state.

The odd winter weather pattern led to record maximum temperature in the state's northwest.

Six weather stations had new August maximums on Tuesday with Tibooburra and Wilcannia both reaching 33C.

But warm clothing will be needed again in the coming days. A cold front from the southeast will bring cooler conditions from Wednesday afternoon.

The wind looks set to stay for a few more days, Ms Barr said.

August's warm weather comes on the back of a record hot July in Australia when the mean maximum temperature was 2.62C above average and 0.66C above the previous record set in 1975.