People flocked to beaches, rivers and lakes yesterday as much of the South Island sweltered on one of its hottest December days.
The mercury reached 34.6degC in Dunedin's Octagon about 2pm, believed to be a record for December.
But this could not be confirmed because of incomplete records.
At Dunedin Airport, the 33.1degC high surpassed the 32.2degC record set in 1990.
Records have been compiled at Dunedin Airport since 1962.
Other areas in the South Island were also feeling the heat.
Oamaru reached 31.9degC about 2pm, breaking the December record of 31.7degC set in 1999.
Balclutha hit 30.4degC, Alexandra 29.9degC and Queenstown 27.7degC.
Christchurch recorded New Zealand's high yesterday with 36.1degC, a December record. Ashburton and Timaru (both 35.3degC) also broke December records.
In Dunedin, about 220 locals, holiday-makers and watersports enthusiasts flocked to Brighton Beach, while hundreds flocked to other city beaches.
Brighton Surf Lifesaving head guard Charlotte Ibbotson said it was the first day of the regional lifeguard season in Otago and "lots of families'' made the most it.
"It's been an excellent way to start the season. Hopefully, it will stay like this.''
Mosgiel mother Amanda Thode, who was at the beach with children Harrison (8) and Sophie (7) and friend Olivia Wallace (6), said they were just enjoying the heat.
Green Island Night'n Day acting manager Susan Hayward said the store sold more than 100 ice-creams.
"It's been an absolute madhouse,'' she said.
Oamaru people headed to the beach in droves and the line for ice-creams at Harbour Tourist Park was out the door.
Park owner Scott Fitzgerald said staff had been "cranking'' out the cool treat.
MetService meteorologist Claire Flynn said the high temperatures were due to an air mass from Australia - bringing temperatures as high as 40decC in Sydney and Adelaide - combining with El Nino's nor'west winds, drawing out moisture and warming when it blew over the Southern Alps.
"Today has been the hottest December day since [records began],'' Ms Flynn said.
"[But] you've got a cool front coming up the South Island [and] it's going to be significantly cooler.''
It would be a shock to many today when Dunedin and Queenstown were expected to reach just 17degC, Dunedin Airport and Oamaru 18degC and Balclutha 14degC, Ms Flynn said.
Alexandra was expected to reach 20degC.
The MetService last night issued a weather watch for severe northwest gales for exposed parts of Otago.
