It was a cold start for Pukaki, which recorded an overnight temperature of -3.1 degrees Celsius.
Otago had its chilliest start of the year so far, with overnight temperatures of -0.9degC in Dunedin, -0.5degC in Alexandra, while Queenstown recorded its coldest morning of 0.2degC, MetService tweeted.
A front moving over the South Island had introduced a lot of cold air into the region, sinking the mercury lower, MetService meteorologist Mmathapelo Makgabutlane said.
"What that did is it brought in a lot of cold air behind it, and the sky was fairly clear overnight, so that served to further drop temperatures.
"And then with that we saw a cold morning in Otago, and generally over the lower South Island this morning."
Tuesday was also expected to be a chilly start for the South Island, Makgabutlane said.
"We've got another cold front that moves across the South Island today, so another cold morning to be expected, and even some possible snowfalls overnight tonight into tomorrow morning down to about 600 metres."
A road snowfall warning is in place for Porters Pass in Canterbury on Tuesday.
Meanwhile, MetService has issued a a strong wind watch for the Canterbury High Country for Monday.
- RNZ and ODT Online
