Sydney, March 25 : The Australian Bureau of Meteorology (BOM) on Saturday issued a warning of severe thunderstorms in multiple parts of New South Wales (NSW), just hours before the Earth Hour events kick off in the state at 8.30 p.m. "Severe thunderstorms are likely to produce heavy rainfall that may lead to flash flooding, large hailstones and damaging winds in the warning area over the next several hours," the weather bureau said in a statement. The BOM mentioned several locations that may be affected, including Tenterfield, Glen Innes, Inverell, West Wyalong, Ashford and Cowra, reports Xinhua news aency. Across the state, the Goulburn Airport recorded 31 mm rainfall in 30 minutes to 11.11 a.m., with Forster and Tuncurry having seen 65-70 mm rainfall within three hours due to persistent storms. In its weather update released on Friday, the BOM forecast "widespread showers and thunderstorm activity" across eastern parts of NSW where some storms could be severe with large hail, damaging winds and heavy rainfall. Due to the rain forecast for Saturday, the Sydney Observatory had to cancel its Earth-Hour-themed event. It featured telescope viewings, talks from astronomers and music performances to help Sydney residents enjoy the night sky, as the city was expected to power down and dim its lights for the annual environment protection movement. Starting as a light-out event in Sydney, Australia in 2007, the Earth Hour, organised by the World Wide Fund, has become one of the biggest grassroots activities with participants coming from all over the world. The Earth Hour event will take place in Australia's Sydney on Saturday, lasting from 8.30 p.m. to 9.30 p.m. /IANS