The NSW government said severe weather in the past 48 hours had battered the Central West, North West Metropolitan, Illawarra and South Coast areas.
Police Minister Michael Gallacher said the Blue Mountains, Oberon, Shoalhaven and the Wingecarribee Shire had been declared natural disaster zones.
"Severe winds have covered much of these regions and this has caused significant damage to these communities," Mr Gallacher said in a statement on Thursday.
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"Today's natural disaster declarations trigger a range of assistance measures for those people who have been directly impacted."
The wind had damaged buildings, parks, reserves and critical infrastructure.
"This declaration will mean help is on hand for residents, primary producers, business owners and councils," Mr Gallacher said.
