Poached eggs, jellyfish, dumplings, cauliflower and cricket balls - these are all words that have been used to describe the giant hailstones that rained down across Sydney and the Central Coast on Thursday evening.

The hail battered Sydney in what has been described as the worst hail storm in 20 years, smashing cars and windows across the city.

As well as round, white-coloured balls, flatter hailstones that appeared to have a white core, a clear centre and white edges were photographed across the city.

Bureau of Meteorology forecaster Craig Ryan said the hail forms as a small white ball, and is surrounded by a lot of water content in the cloud. An updraft of air helps the hail develop in size by keeping it in the cloud.