The mercury could touch 30degC in parts of Dunedin and the Taieri on Sunday.
MetService meteorologist Ashlee Parkes said a persistent ridge of high pressure would bring settled weather across much of New Zealand from tomorrow through to next Tuesday.
Temperatures would sit in the low to mid-20s for much of Otago and Southland tomorrow — the exception being Wanaka and Alexandra, which are expected to reach 27degC and 28degC respectively.
"But then we have another frontal feature that is going to push on to the western South Island on Sunday evening into next week.
"Although this frontal feature will bring rain to Fiordland and Westland, it will stick to the west and will create a Foehn effect [a warm, downslope wind] in eastern areas, bringing dry and warm air, which will see those temperatures rise on Sunday."
Temperatures would reach 27degC in Dunedin, Oamaru and Alexandra on Sunday, and 29degC in Mosgiel.
"Coastal and Central Otago will be hot. Even Invercargill will be slightly warmer than usual for this time of year, with 25degC on Sunday."
Temperatures on Monday and Tuesday next week are expected to remain in the mid to high 20s in Dunedin, Mosgiel, Oamaru, Alexandra and Wanaka, and in the low to mid-20s in Queenstown, Clutha, Gore and Invercargill.
However, winds were expected to turn more southerly by Wednesday, bringing rain and temperatures in the teens back around the southern regions on Wednesday and Thursday, she said.
