Yesterday's freezing morning temperatures crept up a degree or two on Sunday's figures, and today's were a few notches higher again.
At 6.30am today, MetService reported Dunedin was 2.1degC, Queenstown was 0.7degC, Alexandra was 4.6degC and Wanaka was 3degC.
The New Zealand Transport Agency issued a general caution for black ice in parts of Central Otago.
MetService meteorologist Ciaran Doolin said temperatures tonight would be ''quite a different story'' from the past couple of days, with lows across Otago staying above zero, and a 7degC overnight low in Dunedin.
''There may be a frost in some places, but it will be considerably less widespread, and won't be as bad.''
The weather would warm up as the week went on, because of a northerly flow developing over the country, Mr Doolin said.
Alexandra was New Zealand's coldest town yesterday, recording -7degC between 2am and 8am, and a maximum of 4degC during the day.
Wanaka was -5degC at 2am and 5degC at 2pm, Queenstown -6degC from 6am to 8am and 4degC at 2pm, and Oamaru -3degC from 4am to 8am and 7degC at noon.
It was not much better in Cromwell, which had fog until after noon. Shallow edges of Lake Dunstan had stretches of ice, and trees were laden with hoar frost in Cromwell, at Lowburn and near Tarras.
The cold snap in the Mackenzie Basin this time has been less severe than last month.
The temperature in Omarama got down to -8.4degC on Monday morning before rising to a high of 4.3degC, and Twizel's temperature ranged from -9.6degC to 3.7degC. Three weeks ago, after heavy snow, Omarama recorded -22degC.
Busy time for plumbers
The frigid weather had plumbers run off their feet. Foley Plumbers co-owner Craig Foley, in Dunedin, reported up to 20 times as many frozen pipes than in a usual winter.
''We had 40 jobs in today, and probably had about 20 or 30 during the weekend as well.''
A normal number of call-outs for frozen pipes over a weekend was two, he said.
Two other plumbers were too busy to comment yesterday.
One plumber said afternoons were the busiest time, as ice in burst pipes thawed.
''I'm sorry, I have to go, because of all these burst pipe [jobs].''
A burst pipe turned Cosy Dell Rd and Regent Rd in Dunedin into a skating rink yesterday, when leaking water froze into a sheet of slippery ice.
Twizel plumber John McGartland said he and a plumber he brought in from Timaru to help him out had been working ''non-stop'' since the snow.
''You try and have a day off but something else happens.
''You've got to turn out. You can't say, `I'm not coming'.''
Several holiday home owners visiting Twizel in the school holidays had uncovered plumbing problems, mostly burst water pipes, Mr McGartland said.
There had also been instances of hot-water tanks splitting, and waste pipes freezing up.
The northerly change is expected to bring rain to some parts of Otago tomorrow.
There is a heavy rain warning for South Westland from this afternoon. Niwa figures released yesterday show Haast had its fourth-lowest July maximum temperature (6.1degC on the 6th) since records began in 1949.
Dunedin had its second-lowest July minimum temperature (-3.1degC yesterday) since 1947, Balclutha also its second-lowest (-6.1degC yesterday) since 1964, and Alexandra its fourth-lowest (-8.7degC on Sunday) since 1983.
