The year's rainfall up until 9am yesterday was 126.2 millimetres, 8 millimetres below the previous half-year record low of 134.5 millimetres set in 1967.

The rain that fell later yesterday was not included in the half-year total, as the bureau applies a 9am cut-off time on the last day of the month when recording rainfall.

The bureau's Victorian climate services manager, Harvey Stern, said Melbourne had not recorded above-average annual rainfall since 1996. "It is going to take many years of good rainfall to remove these deficiencies," Dr Stern said.

Melbourne Water said the city's dams had received about half the average inflow since the start of the year, with the reconnection of the Tarago reservoir last week providing the only real boost to water supplies this year.