Qantas Airways and Virgin Australia, Australia’s biggest airlines, have together cancelled at least 55 domestic flights in and out of Sydney on Wednesday, the airport’s website showed.

Some international flights have been delayed.

Sydney’s train services have also been disrupted, with authorities urging people to avoid non-essential travel.

“Be really careful. It’s really wild out there, if you can delay travel, please do so,” New South Wales state Emergency Services Chief Superintendent Dallas Burnes told ABC News.

“As people wake today and see the damage from last night, we’re expecting a very busy day.”

A coastal low-pressure system, described by meteorologists as a “bomb cyclone”, smashed Australia’s southeast coast overnight with wind gusts of more than 100 kph, uprooting trees and damaging power lines.

Roughly one month’s worth of rain fell over six hours in some regions.

The weather phenomenon forms quickly and causes air pressure to drop significantly within a short period of time.

More than 35,000 properties are without power in New South Wales, Australia’s most populous state, after the storm overnight, outage data showed.

Several roads in the state’s Illawara region south of Sydney have been closed due to flooding and fallen trees.

Evacuation orders were issued due to coastal erosion in the Central Coast region, while dozens of warnings remain for wind damage and flash flooding.

Conditions are expected to worsen through Wednesday before the system eases and move into the Tasman Sea, and then track toward New Zealand on Thursday.

New Zealand’s National Institute of Water and Atmospheric Research said the low-pressure system could bring heavy rain and strong winds to the country’s North Island on Thursday and into the weekend.