Temperatures in Canberra reached a maximum of 31.8 degrees, prompting many people to cool off in pools and waterways around the capital.

Dickson Aquatic Centre was forced to turn away hundreds of customers who had not secured a booking.

Manager Chris Graham said the pool would usually host up to 1000 patrons at a time but was now limited to 500 people in timed sessions because of coronavirus restrictions.

"Five-hundred in here is a pleasant crowd, there's plenty of space. It was a lovely day," he said.

Mr Graham said the staff were still battle-weary from last summer when all swimming lessons had to be cancelled due to bushfire smoke, leading to $65,000 in fee refunds. This year lessons were able to go ahead despite storms in the first week of January.

He encouraged people to visit the centre's website to book a session or find information before calling reception and to consider the weather forecast when deciding which day to book.

"Come on the days where it's 26-27 degrees when it's really pleasant," he said.

"Unfortunately everyone wants to come when it's 30 degrees."

Meteorologist for the Bureau of Meteorology Melody Sturm said a high pressure system to the south-east over the Tasman Sea and northerly winds were combining to create warm and sunny weather in the ACT and surrounds.

The bureau was expecting sunny days and temperatures in the low-to-mid thirties for the first part of the week.

"The average temperature for Canberra is 28 degrees so that's quite warm and you'll feel it," Ms Sturm said.

Daytime temperatures in Canberra are expected to reach 33 on Monday, 34 on Tuesday and 35 on Wednesday.

Canberrans would also notice hotter minimum night temperatures of 16 to 17 degrees on Tuesday and Wednesday, potentially making it more difficult to sleep.

Ms Sturm said a change may be on the way by Thursday, bringing a chance of showers and thunderstorms.

ACT Health urged Canberrans to watch for early signs of heat stress, including headaches, dizziness, faintness, nausea and vomiting.

ACT Health also issued COVID-19 safety advice for those flocking to pools, including using hand sanitiser, not sharing pool equipment with people from other households, minimising touching surfaces, staying home if unwell and getting a COVID-19 test if you have symptoms.

"Please make sure you keep hydrated and stay safe if you are heading outdoors or to a testing clinic with warmer temperatures forecast for the week ahead," ACT chief health officer Dr Kerryn Coleman said.