Sydney is in mop-up mode after a "one-in-100-year" event poured more than 100mm of rain across the city.

Insurance Council of Australia general manager of communications Campbell Fuller said insurers had already received more than 1600 claims, estimated at $10 million, due to Wednesday's storm.

SES crews clear roads and assist with damaged homes. Credit:Ausgrid

"These claims are mostly for roof and car damage and is not an unusual level of claims lodgement for a Sydney region seasonal storm," he said.

"The Insurance Council of Australia will continue to monitor the number of claims lodged over the next few days."