Sweltering conditions are on the way for parts of the South Island this week

Christchurch can expect a soaring 35 degrees tomorrow - 12 degrees above the city's average temperature for this time of year.

MetService meteorologist Alwyn Bakker says the city's looking at three days in a row with temperatures more than five degrees above average.

He says the heat and fine weather is due to a high pressure ridge moving across the country.

Timaru is also headed for a scorching 34 degrees tomorrow, with Hastings and Gisborne due for the same on Wednesday.