Families in parts of the northern beaches are being advised to make alternative dinner plans with a blackout currently affecting more than 30,000 homes and businesses.

About 4.30pm Tuesday, Ausgrid tweeted that emergency crews are working to restore power to 31,000 homes and businesses in Avalon, Mona Vale, Newport, Warriewood, Palm Beach, North Narrabeen, Elanora Heights, and surrounding suburbs.

The cause of the outage is not currently known.

Customers affected "may want to make alternative plans for dinner", Ausgrid said in another tweet, "as we’re estimating power won’t be restored until about 8pm".

"We are working as quickly as possible to restore power safely. Sorry for the disruption."

More to come.