Victoria should brace itself for extreme weather over the next few days, with the bureau forecasting damaging winds, flooding rains and snow before conditions clear up for Melbourne Cup day.
The forecasts prompted the Department of Health and Human Services to warn of an elevated risk of thunderstorm asthma for the first time this season.
The risk for Saturday is moderate in Northern Country, North East and West and South Gippsland, and low throughout the rest of Victoria.
The department rated the risk of epidemic thunderstorm asthma on Friday as high in the Wimmera region, and moderate in the South West, Northern Country, North Central, Mallee and Central regions, which takes in Melbourne.
The risk had passed by late Friday afternoon, but the department said people should remain vigilant.
Ten people died after a cool change blew through Melbourne on November 21, 2016, sparking asthma-like symptoms in thousands across the city.
Melburnians felt some relief on Friday night when temperatures plummeted from 29 degrees Celsius to 19C in 10 minutes about midnight and a low of 15.8C overnight.
Bureau of Meteorology senior forecaster Rod Dickson said a severe weather warning for damaging winds and heavy rainfall remained on Saturday for central and eastern Victoria, but damaging winds were easing for Melbourne and a dust haze had cleared.
A cool change is tipped to move through the state this weekend, with the bureau forecasting a top of 21C for Melbourne on Saturday with thunderstorms and the possibility of flash flooding threatening to disrupt Derby Day festivities at Flemington racecourse.
Mr Dickson said many rainfall totals across the state for Saturday would typically be between 10 and 20 millimetres, including Melbourne, but parts of north-eastern Victoria could be drenched with up to 50mm.
More showers are expected on Sunday, and on Monday snow is expected to fall in alpine areas as a mass of cold air moves across the state.
Mr Dickson said the good news for racegoers was that the weather would clear up for Cup day, with a partly cloudy day of 22C tipped.
That would be a welcome change from Cup day last year, when wet and windy weather played havoc with racegoers' travel and fashion plans.
