But more than 30mm could fall in the city tomorrow and Friday, providing a boost for the start of summer.

Last weekend, 63mm of rain was dumped on the city, the highest total in 11 months.

But according to yesterday's water storage data released by Central Highlands Water, levels had dropped to 16,961ML, down from 17,019ML last week.

CHW spokeswoman Nicky McMaster said the drop was due to last week's hot weather, causing between 50ML and 80ML of evaporation.

She said there had also been extra water use under stage 4e water restrictions.

"We did have a really good downfall, but the inflows won't continue to run if they're followed by some warm days," Ms McMaster said.

"If we have some good rainfall this week, hopefully we may notice a difference next week."

While today will be sunny in Ballarat with a top temperature of 25C, tomorrow may be slightly muggy, with a top of 26C and scattered showers in the morning.

The Bureau of Meteorology also expects a chance of thunderstorms from midday, with similar weather expected on Friday.

Bureau duty forecaster Rod Dickson said there was a low pressure system over Queensland which contained a lot of moisture and would drag down to the lower areas.

"We can probably expect some good widespread falls of 10mm to 20mm across the state, but there will be some heavier falls with that as well, particularly about the ranges and in the south-west," he said.

"We can expect upwards of 30mm in those ares if that moisture comes down."

Saturday, Sunday and Monday will be around 15C, but the showers will remain.