The Met Service issued a yellow weather warning for high temperatures forecast for Friday, when temperatures inland are expected to reach 40 degrees Celsius.
The yellow warning will be in effect from 11am until 4pm.
The Met Service announcement said temperatures are expected to be much more bearable in coastal areas, at around 33 degrees Celsius.
The weekend is expected to see mostly clear skies, with increased clouds expected come Monday noon.
Temperature levels are expected to show a slight rise on Saturday, going above the average levels for the period, particularly inland and in mountain areas.
The heat is forecast to begin retreating early next week.