Many parts of the country have gone without rain now for weeks.
Some rain has fallen in Christchurch today, the MetService says, breaking the city's longest recorded dry spell.
Christchurch had a record stint without rain since observations started at the airport 74 years ago - 47 days with less than 1mm of rainfall.
Interestingly, the city also recorded the wettest Christmas Day on record in 1909, when 59.77mm of rain fell.
Forecast rain has started to fall in parts today and more rainfall is forecast this week for the east of the South Island and many parts of the North Island.
The National Institute of Water and Atmospheric Research said historical data suggest Wellington and Christchurch were the main centres most likely to experience a dry Christmas Day. Auckland and Hamilton are the least likely.
Niwa analysed 30 years of Christmas records and found the capital and Christchurch only had four wet days on December 25 - once every 7.5 years.
Wellington has not had a wet Christmas Day since 2002.
Niwa forecaster Ben Noll said the number of wet days in some centres might surprise people.
"There's a perception that Christmas in New Zealand is more often soggy than dry.
"We call Christmas 'wet' if 1mm or more of rain falls in the 24 hours beginning at 9am on the 25 and ending at 9am on the 26.
"Of course, history is useful for showing us patterns but it doesn't tell us exactly what Christmas Day 2017 will be like in the main centres."
Soil moisture levels continue to run below or even well below normal across nearly all of New Zealand. Unfortunately only the West Coast is expected to see any meaningful improvement through next week.— NIWA Weather (@NiwaWeather) December 9, 2017
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In the North island, Auckland and Hamilton had a wet Christmas Day on 11 occasions.
Soil moisture levels - used to track drought conditions - are not forecast to significantly improve, even with fresh rainfall. Only Fiordland and the West Coast are expected to receive significant falls.
MetService driest spells on record/days without rain:
- Queenstown - 56 days
- Christchurch - 47 days
- Blenheim and Hamilton - 43 days
- Tauranga - 42 days
- Napier - 39 days
- Wellington - 34 days
- Auckland - 32 days
- Westport and Hokitika - 32 days
- Dunedin - 30 days
- Invercargill - 24 days