Footage shows a dramatic lightning storm seen above Sydney in New South Wales, Australia, as at least one person was killed in the storm. Officials said that an unstable airmass combined with an upper trough produced wild weather across large swathes of the state late Wednesday.

Wild weather is expected to continue through the weekend, with ongoing thunderstorms on the east coast and a tropical cyclone developing just off the coast of Western Australia.

Authorities declared a natural disaster Saturday in parts of eastern Australia where gales have toppled trees and knocked out power to tens of thousands of homes. Heavy rain, lightning and winds as strong as 100 kph have swept across Sydney and other areas of New South Wales since Wednesday.

A huge line of storms crossed New South Wales overnight, causing power outages, flash flooding and almost 2 million lightning strikes.

SYDNEY, Jan 18 — Authorities declared a natural disaster Saturday in parts of eastern Australia where gales have toppled trees and knocked out power to tens of thousands of homes. Heavy rain, lightning and winds as strong as 100 kilometres per hour (60 miles per hour) have swept across Sydney and other areas of New South Wales since Wednesday.