The rain is here. 

The Bureau of Meteorology says people living or working along rivers and streams must monitor the latest weather forecasts and warnings and be ready to move to higher ground should flooding develop.

It was 18 degrees in Warrnambool at 3.40pm and it felt like 16 degrees. 

The city has had 4.6mm of rain since 9am. There is a 60 per cent chance of it continuing over the next hour. 

Earlier:

A big thunderstorm could be on the way, leading to flash flooding across parts of the south-west.

The Bureau of Meteorology has issued a flood and severe thunderstorm warning for Warrnambool, with rainfall totals of 50 to 80mm possible in coastal areas.

Elsewhere across the flood watch area, totals of 15 to 40mm are forecast for the south. 

The BoM says severe thunderstorms affecting other parts of the state has seen rainfall rates of up to 13mm in five minutes during the early hours of Saturday morning. 

SES has advised people to keep clear of creeks and storm drains; don't drive, ride or walk through flood water; stay indoors if possible, avoid using the phone during the storm; and if you are outside, avoid sheltering under trees. 

Across the south-west, winds will be south-easterly 15 to 20km/h tending north-west to north-easterly in the middle of the day. 

Daytime maximum temperatures are expected to reach the low to mid 20s. 

Further showers and storms will follow for the weekend.