ACT health has issued a public health alert as the heat is set to crank up to 37 degrees on Saturday and 38 on Sunday and Monday.

But it's not just our two-legged friends we need to look out for as things heat up, with our four-legged companions feeling the heat too.

For dog groomer Nikki Fallon, as soon as the temperature starts to rise, the phone starts ringing off the hook.

Ms Fallon has had an extra busy Summer this year after coronavirus lockdown and working from home led to an increase in pet adoptions.

"As soon as we have the hot weather and people see their dogs starting to pant, because they haven't thought about it, we do get a major influx," Ms Fallon said.

"We're getting quite a few calls every day and messages.

"People who are new to dog ownership, a lot of the COVID puppies, are now realising they should have booked in a groomer 12 months ago."

Her mobile grooming service, Doggy Day Spa Canberra, has been extra busy this week with heatwave conditions to descend on the capital and much of NSW for the Australia Day long weekend.

For pups with an extra thick coat, or a 'doona' as Ms Fallon calls it, grooming can be a way to help them out in the worst of the summer heat.

Veterinarian Eamon Ryan from the Belconnen Veterinary Centre says pets should be kept in the shade during hot weather, and ideally in an air-conditioned environment.

He said common-sense was key and urged people not to walk their dogs during the heat of the day and be mindful of how the ground was when they do step outside.

Putting your pup in a pool of cool water can also help keep them comfortable, but Dr Ryan said owners should avoid using ice in case it caused a rapid temperature change.

Bureau of Meteorology forecaster Alex Majchrowski said a cool change was expected to come through on Wednesday, bringing cooler temperatures and possible showers.

"We have a high pressure system over the Tasman and a trough in the west of NSW and together they act to draw in the heat from the interior of the state," he said.

"[That will] see severe heatwaves conditions brought to Canberra over the next several days."

ACT chief health officer Kerryn Coleman said hot weather posed risks, particularly to vulnerable people including the oldest and youngest Canberrans, and pregnant women.

"Everyone can be susceptible to heat-related stress and illness in the heat," she said.

"That's why people need to stay hydrated and stay cool. This is particularly for older people, pregnant women, young children and babies, who are most at risk."

"Look out for the early symptoms of heat related stress including headaches, dizziness, faintness, nausea and vomiting.

"In babies, signs of heat stress include irritability, restlessness and a reduced number of wet nappies."

People preparing for outdoor Australia Day festivities have been urged to be cautious and prepare for the extreme conditions. The day is forecast to be 35 degrees with a low of 23.

ACT ambulance service chief officer Howard Wren said people would need to take extra precautions when enjoying the outdoors.

"It is particularly important people seek shade during the hottest parts of the day, drink plenty of water and limit their alcohol consumption," he said.

Cooler weather is set to return late next week, with a top of 28 degrees forecast on Wednesday and the chance of up to 5mm of rain.

On Thursday, a high of 22 and low of 14 is expected with up to 8mm of rain possible.