Christchurch set for year's coldest night

Surface flooding in Pages Road in the Christchurch suburb of Bexley today. Residents have been advised the water is contaminated and should be avoided. Photo / Paul Harper

Christchurch is set to be hit by its coldest night of the year as thousands of earthquake hit residents head into their third week without electric heating.

WeatherWatch.co.nz has predicted near frost level temperatures in the city, with an overnight low of just 3 or 4 degrees Celsius.

Its head analyst Philip Duncan said the cold snap was because of a southerly change dropping temperatures across New Zealand.

"Tonight winds will ease and clouds will clear Canterbury with the mercury expected to fall into the low single digits," he said.

That prediction comes as lines company Orion deals with a setback in its efforts to restore power to Christchurch.

A statement issued by the company today said 13,400 residents are still without power in the city.

More than half of those are in the eastern suburbs including Brighton and Dallington, while about 4700 properties in the city centre were also without electricity.

Work has been delayed by the failure of the only major cable still operating at its Brighton substation, the company's statement said.

Its aim of restoring power to 99 per cent of customers by the end of today was now in doubt,

"The fault was located early afternoon and will take approximately 12 hours to fix.

"Last night's failure at Brighton highlights just how fragile the network is. It is crucial that customers continue to do everything they can to conserve electricity, so we can share supplies around."

WeatherWatch said the cold temperatures are unlikely to last long - predicting both daytime highs and overnight lows will creep up from Tuesday onwards.