Canberra is set to receive up to 30mm of rain across Friday with the Bureau of Meteorology forecasting a possible storm in the afternoon.

Bureau forecaster Abrar Shabren said if a storm does hit it would likely not bring severe or damaging conditions but be a "garden variety" system.

"There is a lot of moisture hanging around with the trough that has moved across," he said.

"[There is also] a ridge of high pressure the state is sandwiched between with a trough to the west and north of the state that is dragging a lot of moisture causing the unsettled conditions."

Rain fell through most of Thursday into Friday morning. Canberra Airport recorded 21.6mm before 9am on Friday.

A top of just 19 was forecast for Friday, with much of the ACT staying around the high teens, Mr Shabren said.

However, throughout Saturday and Sunday the temperature will increase up to 27 degrees while the rain remains, making for very humid conditions.

Mr Shabren expected the wet weather would ease by Tuesday with sunny days to return on Wednesday.

A severe weather warning has been issued for heavy rain in parts of NSW west of Canberra, stretching from Ivanhoe to Tumbarumba.

"A cloud band with embedded thunderstorm activity associated with tropical moisture drawn over NSW by a trough over the west of the State has the potential to produce locally heavy rainfall," the Bureau warns.

"Widespread totals of 25-50mm of rain expected across the warning area today with locally heavier totals of 40-70mm possible in a 3 to 6 hour period, especially with thunderstorm activity."

In the 6 hours to 2am Condobolin recorded 66mm.