Many families were out and about enjoying the sunshine and celebrating at Father's Day picnics.

Parking was bumper to bumper at various lakeside locations such as Weston Park, the Yarralumla Yacht Club and Lennox Gardens.

At Yarralumla Beach, Clinton McCarthur and his two daughters Penny, 4, and Alice, 3, were having a jolly time playing in the water.

They were celebrating Father's Day with extended family who looked on as Penny and Alice built sandcastles and happily splashed around.

Nearby, the Willis family were watching as their dogs ran amok in Lake Burley Griffin.

"We came down to enjoy the weather and give the dogs a bit of a swim now that we have some warm weather," David Willis said.

Mr Willis was celebrating with his children but was also video-chatting with his father who lives in Perth.

"It was good to chat, as obviously I can't see him at the moment," he said.

Canberra reached a forecast maximum temperature of 17 degrees on Sunday, according to the Bureau of Meteorology.

And it will be even warmer on Monday and Tuesday with tops of 20 degrees and 21 degrees expected, respectively.

"A warm high pressure system is sitting at the Tasman Sea now and what that means is we have a northerly air stream across the south-east of Australia, including the ACT and plenty of sunshine," BOM meteorologist Neale Fraser said.

But Mr Fraser said the weather is expected to cool on Wednesday and the territory could receive up to 10 millimetres of rainfall.

"We're expecting showers to roll in from a front coming through on Wednesday," he said.

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"Wednesday is the only day of any real rainfall for Canberra and it starts to warm up again ahead of next weekend."

By Saturday the temperature is forecast to reach 18 degrees.

Over the coming weeks temperatures in Canberra were likely to range from 14 degrees to 21 degrees, Mr Fraser said.