The 1999 Sydney hailstorm was the costliest natural disaster in Australian insurance history, causing extensive damage along the east coast of New South Wales.

The storm developed south of Sydney on the afternoon of Wednesday, 14 April 1999, and struck the city's eastern suburbs, including the central business district, later that evening.

A weak cold front was moving north along the coast, and moderate precipitation was falling over the Blue Mountains, southwest of the city.

The meteorological reports and figures, however, suggested that the general atmospheric conditions were "not conducive" to support the formation of a major thunderstorm in the region.

[10] Historical records show that the formation of severe thunderstorms for the time of day and year had been rare, and it was improbable that they would maintain their intensity and cause significant damage.

[15] 'Severe' is a classification used by the Bureau of Meteorology for thunderstorms which meet a specific criteria, namely producing hailstones with a diameter of 2 cm (0.8 in) or more, wind gusts of 90 km/h (56 mph) or greater and flash flooding, or tornadoes.

[17] The Bureau of Meteorology had not issued warnings for Sydney Airport, located on the northern shore of Botany Bay, or the rest of the eastern suburbs to prepare for large hail.

The Bureau of Meteorology had concluded that the storm would weaken after heading across Sydney Harbour, believing it was dissipating and would therefore not produce any more substantial hail as it moved northward; therefore it did not issue warnings for the northern suburbs.

[5][6] The storm was the costliest natural disaster ever to hit Australia in terms of insured losses, surpassing the 1989 Newcastle earthquake by around A$600 million.

[24] Twenty-three aeroplanes and helicopters at Sydney Airport were reported as having incurred notable damage from the hail, caused by the inability to place them under hangars in time to avoid the storm.

This has been significantly attributed to a lack of warnings from the Bureau of Meteorology, who had expected the storm to continue moving further out into the Tasman Sea in the north-northeasterly direction in which it had previously been travelling.

[24] The storm caused one fatality; a 45-year-old man, who was fishing about 100 metres (300 ft) from the north shore of Dolans Bay in the Port Hacking estuary, was killed when his boat was struck by lightning.

[5] Fifty injuries were recorded, caused by flying objects, road accidents due to poor visibility and smashed windscreens and other factors.

[4][26] One month after the disaster, the main priority of the emergency services was ensuring that temporary fixes remained in place, as Sydney suffered further adverse weather in the period immediately following the storm.

[12] Construction of infrastructure for the 2000 Sydney Olympics in the city's west at the time meant there was a deficiency of tradespeople who could be contracted to repair roofs and windows.

Estimates put between 45,000 and 50,000 tradespeople in Sydney at the time of the storm, yet owing to high demand "companies were quoting householders A$14,000 or more for roof repairs which would normally cost $3,000.

"[26] The situation led to a warning from the Minister for Fair Trade, John Watkins, on the day following the storm, urging homeowners to ensure that tradespeople working to repair homes were fully qualified and legitimate.