Holiday parks are warning to book early, with many expecting the summer to be even busier than usual.

Figures from the Holiday Accommodation Parks Association shows confidence at 78 percent, while 48 percent of owners are expecting higher demand than last year.

Chief executive Fergus Brown says the growth isn't just being driven by New Zealanders, there's also a spike in international visitor numbers.

He says there are more flights coming in from China, with big growth in North America and Australia as well.