The Christmas barbecue might need to be cooked beneath an umbrella this year - but any rain will be limited to brief showers.
The long-range forecast is showing a front passing across the country on December 24 and 25.
MetService forecaster Daniel Corbett said it was too early to know exactly when the rain would pass but he was confident the weather system would be fast-moving.
"It's most likely a case of one or two showers. People should bear that in mind and remember to pack a brolly in the picnic basket."
The weather system would pass by Boxing Day, Mr Corbett said.
The weather in the lead-up to Christmas Eve was looking fine and warm, Mr Corbett said.