Flooding, rain, wind set to lash NSW EXTREME weather including heavy rain, gale force winds, dangerous surf and flash flooding is set to hit NSW on Monday. The Bureau of Meteorology (BoM) late on Sunday night issued a severe weather warning for Sydney, the midnorth coast, Hunter region, Illawarra, south coast, central tablelands, southern tablelands and Snowy Mountains. BoM is warning of damaging winds, heavy rain, king tides, and damaging surf on Monday as the result of a trough sitting off the coast. It says heavy rain and isolated thunderstorms may lead to flash flooding in many parts of the state. Winds are predicted to reach 100 kilometres per hour in Sydney, the Illawarra and the Hunter, BoM advises. The SES said hundreds of emergency staff and volunteers were ready to respond to the extreme weather due to hit around lunchtime Monday. The SES expects the worst hit areas to be Sydney and the Illawarra where roof damage and fallen trees are expected. BoM's latest weather warning update is due at 5am (AEST).