A heavy soaking is on the way to the capital to welcome in the start of summer.
The Bureau of Meteorology issued a severe weather warning on Friday morning predicting heavy rain and damaging winds which could lead to flash flooding.
The system is expected to sweep across Australia's south-east, with an "unprecedented" amount of rain expected over Victoria.
ANU climatologist Clem Davis said Canberrans could expect the rain to set in late on Friday after the mercury hits 29 degrees Celsius.
"And on Saturday in Canberra we're expecting between 35 and 60 millimetres, with heavy falls and the chance of a thunderstorm," he said.
Temperatures are expected to fall on Saturday to a top of 23C.
A warm and humid air mass has been building over the west of New South Wales for the past couple of weeks.
That will interact with a cold front that is forecast to move through NSW over the weekend, forming a low over the inland and generating widespread heavy downpours with embedded thunderstorms.
Gale-force winds are also forecast over the alpine peaks.
Long-term weather forecasts are predicting above-average rain in the region this summer.
Mr Davis said rain over the coming days would increase the soil moisture, promoting rapid fuel growth.
"That may work to reduce the fire danger ratings until those conditions dry off," he said.
"Bushfire risk will then be driven by whether we have heatwaves or whether we continue to get rain."
