Tradies are being urged to stop work today as Sydney is set to be hit with scorching summer temperatures, with the mercury pushing close to 40C.

Tradesmen across the city are well within their rights to put down their tools today as hot weather blasts the state, resulting in dangerous working conditions.

While western Sydney is no stranger to summer days in the high-30s or low-40s, the CBD is often far cooler aided by winds coming off the Pacific Ocean.

However Tuesday’s heat is set to be relentless across the entirety of the city with the CBD reaching 37C and Penrith, in the west, 38C. Brisbane will be hot too, reaching 35C and then 36C on Wednesday.

Once the temperature reaches 35C or above 75 per cent humidity workers should be relocated to a cooler area, under the heat policy produced by the Construction, Forestry, Maritime, Mining and Energy Union (CFMEU).