Australian tradesmen are being told to take the rest of the week off as temperatures continue to soar across the country.

Several Australian states have been experiencing record-breaking heat this week and temperatures are set to rise with some states experiencing 46C.

The heatwave is expected to last until Australia Day, on Saturday, at least.

If temperatures reach 35C, tradesmen have been advised they are within their rights to stop working.

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The nationwide Construction, Forestry, Maritime, Mining and Energy Union (CFMEU) has told its members to avoid working during "dangerous" heat.

"Once the temperature reaches 35C or a humidity level above 75 per cent, there will be an orderly cessation of work and preparations for safe completions of critical tasks currently underway," a guide by the union reads, according to the Daily Mail.

The union wants workers aware of the dangers of "heat stress".

"Sufficient numbers of workers should be engaged to allow rotation of workers in periods of heat."

Employers have to provide easy access to cool drinking water for all workers.

"In addition, rest breaks [to be provided] as needed by an individual. Individuals should not be discouraged from taking needed rest breaks," guide said.

Tradies are also being told to adhere to their "smoko" and lunch breaks, to avoid strenuous activity.