The WA Police Minister Paul Papalia has defended the lack of air-conditioning in the notorious Unit 18 at Casuarina Prison as a heatwave hits the state.

The WA government has come under scrutiny over the treatment of young offenders - many of whom are on remand and have not been found guilty of a crime - with WA's Children's Court president Hylton Quail previously labelling Unit 18 a "barbaric dungeon."

On Friday, Minister Papalia addressed concerns from many that the children in Unit 18 were suffering as heatwave conditions continue to expose WA to temperatures well over 40 degrees, saying a lack of air-conditioning was not a "major issue."

"Generally, the nature of the buildings is adequate to deal with the heat and house people comfortably," he said, as reported by The West Australian.

"A lot of Western Australians don't have air conditioning, so the fact that some prisoners in prison don't have air conditioning isn't a major issue.

"The heatwave is something we're all confronting, and lots of people don't get the opportunity to go to an air conditioning site ... and yet, people manage to deal with it."

Government advice has recommended people stay indoors with their air conditioner or keep a fan on if they have them If they cannot do that, seek a public place, such as a library or a shopping centre to remain cool.

Indigenous youth are over-represented in the state's juvenile justice system.

Mr Papalia said the people in the carceral system were there for a reason: "They've committed offences, they've harmed other Western Australians, and they've been sentenced to time in prison."

Across Australia, almost 40 per cent of prisoners are on remand and either have not been convicted or not been sentenced yet.

16-year-old Indigenous child Cleveland Dodd, who died in Unit 18 last year, was on remand. The government has been blamed for a range of alleged failures that led to his death.

Cleveland's lawyer said in a letter to Deputy Commissioner for Women and Young People, Christine Ginbey, that he was lucky to get more than one hour out of his cell every day and had begun sleeping through the day rather than endure the torment of being locked in a tiny box with nothing to do.

In response, Mr Papalia said at the time: "There's nothing in that letter that was new."

Those who are sent to Unit 18 receive far less time out of their cells than prisoners at other youth facilities, including the much-criticised Banksia Hill. The ABC reported there had been over 20 suicide attempts in just over the first year the facility had been opened.

"It is one of prolonged systemic dehumanisation and deprivation, with no rehabilitative element or effect," President Quail said last year.

58 letters from detainees detailing abuse allegations from both Unit 18 and Banksia Hill Detention Centre were tabled in WA parliament last year, in a facility WA Premier Roger Cook has called a "necessary evil."

National Indigenous Times has reported on a litany of controversies and tragedies in the WA justice system, which has a drastic over-representation of Indigenous people.

These include video evidence of guards at Banksia Hill using banned manoeuvres on children, accusations of callousness from the opposition about the revolving door of youth incarceration in the state, and a continual lack of air conditioning in Roebourne, despite constant calls for it to be installed in Australia's hottest prison.