Canberra weather: Heatwave to hit ACT on Australia Day long weekend

The heat will crank up in Canberra on Friday with a top of 34 forecast before the temperature drops to a low of 14 on Saturday morning.

Severe heatwave conditions are set to follow, with 37 degrees expected on Saturday and 38 on Sunday and Monday.

Bureau of Meteorology forecaster Alex Majchrowski said a 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."

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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.

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 possible.

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