The Minister for Western Sydney Stuart Ayres has warned that residents in the Hawkesbury-Nepean region would have "been in a lot of trouble" had the city's main dam been closer to capacity.

Using the wild weekend weather to defend the NSW government's plan to raise the Warragamba Dam wall, Mr Ayres said communities escaped a severe flood because of the drought.

Outer-western Sydney escaped a severe flood because water levels in the Warragamba Dam were so low, Western Sydney Minister Stuart Ayres says. Credit:Wolter Peeters

The drought had caused the dam's water levels to drop to as low as 43 per cent but then surged to 71.3 per cent as of Wednesday after the city was hit with heavy rain over the weekend.

Mr Ayres, who has been a vocal supporter of the controversial plan to increase the height of the dam's wall by 14 metres, said the region was spared because the dam's levels had been so low.