It issued a flood watch for the catchment area on Wednesday and a severe weather warning on Thursday, while Canberra was set to cop a lot less rain.

Public information officer at the SES Queanbeyan unit, Brent Hunt, said the Queanbeyan river had not risen but he was expecting heavy rain overnight.

"We are staying prepared, we've been working through the day to ensure we are operationally ready to respond to anything that may eventuate today and tomorrow," he said.

"We have a very strong stance on people staying out of flood water, because it puts our volunteers in danger when they have to rescue people, and it's not worth your life or ours for a shortcut or a bit of fun."

BOM senior forecaster Neale Fraser said Canberra would likely avoid most of the 50 millimetres of rain expected to fall overnight in Queanbeyan.

Canberra airport saw 1.8 millimetres of rain on Thursday and was expected to have the same amount on Friday.

Mr Fraser said the heatwave that hit the ACT this week was over – for now.

"It will be a lot cooler tomorrow: 22 for a max temperature, Saturday 23, Sunday warming up again to 26," he said.

"But it will get hot again with [tops of] 30 Monday and 32 on Tuesday."

For emergency assistance call the SES on 132 500, and call 000 immediately for life-threatening emergencies.

For the latest weather forecasts, rainfall and rain level information, see bom.gov.au