A big clean-up operation is underway in Melbourne this morning, after an intense cold front lashed the city with damaging winds. St Kilda and Fawkner Bay recorded winds gusts of more than 110 kilometres per hour, bringing down trees and blocking roads. More than 430 calls for assistance were made, mostly for damage to roofs and fallen power lines. Authorities are warning those in Melbourne to be extra aware of conditions in the coming days, with an increase in the pollen count bringing a heightened risk of thunderstorm asthma. It follows a severe thunderstorm that battered the New South Wales mid-north coast. Wauchope was worst hit with homes there left without power after heavy hail and some flooding. Sydney is expected to receive a drenching this week with rain forecast for most days.