Hail lashed homes in the city's west during the afternoon and emergency services received calls to a total of 37 incidents across the ACT.

Canberrans reported leaking roofs and trees fallen across roads, and Evoenergy restored electricity after brief outages in Curtin, Garran and Hughes caused by branches falling on power lines.

A burst of rainfall in Weston Creek reached 25mm in 20 minutes at 3pm, when hail up to golf ball size was also reported at Holder and Duffy.

Anne Martin, of Chifley, said hailstones had cut through the skylight in her hallway during a heavy 10-minute fall starting at 2.50pm.

"I knew something would happen because they were just hammering the house," she said.

"After that there was this huge deluge of rain."

Holder resident Douglas Allen posted photos to Facebook showing his pergola roof pierced by hailstones.

The weather bureau at 7pm warned the city was not out of the clear as more storms threatened to arrive from west of the ACT.

The Bureau of Meteorology at 6pm said severe thunderstorms had eased in the territory but warned damaging, heavy rainfall could later on Friday cause flash flooding and large hailstones in the region.

The ACT State Emergency Service earlier advised Canberrans to be prepared for the storm.

Goulburn Airport recorded 26 millimetres of rain in half an hour just after 1pm.

A stationary trough over inland NSW had brought warm and unstable tropical air from the north-east of Australia, the Bureau of Meteorology's Rebecca Farr said.

"When you combine that with the summer daytime heating, we have been seeing storms developing in the afternoons on most days," she said.

Thunderstorms can be quite small, but when a line of storms developed a large area would be affected, Ms Farr said.

"The nature of storms is that they can have a heavy downpour in one location."

A storm on Tuesday saw 9 millimetres of rain fall in an hour, power lines damaged and radio broadcasts interrupted.

Along with reports of flash flooding and leaking roofs, a window fell 12 storeys from the Trilogy apartment tower during the storm.

The current trough is expected to weaken in the next few days while a high pressure system establishes itself over NSW and moves in from the west, bringing heatwave conditions to Canberra.

"It's this new high pressure system that will generate the conditions similar to what we saw around Christmas time," Ms Farr said.

The weather bureau has forecast severe heatwave conditions reaching the capital by Wednesday.

Temperatures between 30 and 35 degrees are forecast for the weekend and Monday, before rising to 38 degrees on Tuesday and Wednesday.

The intensity of a heatwave was assessed against what heat had been experienced in the region in the previous month and what temperatures were expected, Ms Farr said.

"It's about how much capacity people have to cope with the heat."

But it was too early to say when Canberra would see more relief from the heat because the severe heatwave conditions were predicted at the end of the forecast period.