"Especially when the sun is out, people come out of their cave and come out for something to eat."
Mr Pou said it was normal for business to pick up over the summer period.
"It should be like this through to March but it depends on people and whether they decide to come out or not."
Nationwide, New Zealanders spent an extra $235 million more this January than in January 2014 - a 5.5 per cent increase.
The Paymark data showed $4.5 billion changed hands by Eftpos in the first month of 2015.
There was also a 9.7 per cent increase in the number of transactions, totalling 94.54 million.
Paymark head of customer relations Mark Spicer said the growth was expected to continue throughout the year.
"Even with low fuel prices pulling the growth rate down, it's a good solid start to the year," he said.
"The increase in the value and volume of transactions in January are good indicators that we can expect continued growth during 2015."
The biggest spending day was Friday, January 30, with $174.3 million processed - up 3.4 per cent on the same Friday in 2014.
Meanwhile, mixed spending patterns were recorded on the two major anniversary weekends in Wellington and Auckland.
A decrease of -0.4 per cent was recorded on Wellington Anniversary weekend, compared to the same time in 2014, while the opposite was true of Auckland Anniversary weekend.
Spending in Auckland and Northland totalled $144 million - up 6.9 per cent on the same three days last year.
Mr Spicer said spending patterns were evidence of Kiwis making the most of the long weekend.
"A jump in spending on accommodation, food and beverages was seen through the Paymark network during this period, evidence that the long sunny weekend was enjoyed by many."
