Flash flood warning to follow scorching spring weather

Pack away your bathers and get your umbrellas ready - summer is set to be rung in with a fierce rainstorm.

As Melbourne breaks records on Wednesday for warm spring weather, we are being asked to brace ourselves for "extreme" rain to hit on Friday.

The city is forecast to be lashed with more than its monthly December rainfall average in just the first two days of summer.

Meanwhile, some areas of the state are expected to cop up to 250 millimetres.

"It's certainly going to be a very wet start to summer," Bureau of Meteorology senior forecaster Richard Carlyon said.

The bureau will release a severe weather warning Wednesday afternoon regarding the slow-moving trough.

Northern Victoria will bear the brunt, with up to 200 millimetres expected to fall in areas. The North-Eastern ranges is likely cop up to 250 millimetres.

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Melbourne is forecast to receive up to 50 millimetres of rain on both Friday and Saturday, almost double December's entire average of 60 millimetres.

Mr Carlyon said rain levels could rise quickly and a flash flood warning was likely for the entire state.

The humid spring weather has led to a build of moisture in the air, paving the way for the heavy rain.

Wednesday's scorcher is the 13th day that has topped 30 degrees before summer arrives in Melbourne.

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At 1.30pm the mercury had hit 34, with a predicted high of 35.

It breaks the previous record of 12 pre-summer days above 30 degrees in 2009.

This story Flash flood warning to follow scorching spring weather first appeared on The Sydney Morning Herald.