The bureau says a high pressure system is sitting over New Zealand, with a low pressure trough over central Victoria.

A cold front will enter western Victoria this afternoon, moving across the state and clearing in the far north-east tomorrow morning.

The bureau says people in fire-affected areas should beware of the potential for landslides and debris on roads, as rainfall-run off may contain soil, ash, trees and rocks.

The State Emergency Service advises people should:

- Not drive, ride or walk through flood water

- Keep clear of creeks and storm drains

- Call your SES unit on 132 500 for emergency help

The warning comes after one local business was forced to close and others received severe flooding and collapsed roofs after thunderstorms lashed Ballarat last night. 

Clothes store Eight Below in Sturt St locked its doors "until further notice" with owner Krissy Papsworth saying she arrived this morning to find her shop flooded and roof on the verge of caving in.

"As soon as I walked in I could smell the water that had gathered in the store," Ms Papsworth said.

"It took a long time to clean up and I've had to close up because it's simply to dangerous to stay open with the roof likely to collapse any minute."

El Artista Hairdressing owner Tania Alsop said she also arrived at work this morning to find her business completely flooded.

"When I walked in there was literally water pouring through the light fixtures," Ms Alsop said. 

An already saturated Ballarat recorded 26mm of rain over night, taking the total rainfall measurement to more than 70mm for the last two days. 

Weatherzone meteorologist Brett Dutschke said it had been more than a year since 70mm of rain was recorded over two consecutive days.

The SES responded to eight requests in the region last night including fallen trees creating traffic hazards in Soldiers Hill, Scarsdale, Springdallah and Elaine. 

Powercor Spokesperson Drew Douglas said more than 750 customers were without power in Mt Mercer early this morning after lightning strikes.