Farmers say evidence of rising temperatures points to a need for better water storage.
The National Institute of Water and Atmospheric Research says weather statistics confirm that 2000 to 2009 was the warmest decade since record keeping began.
The average temperature was fractionally higher than in the 1980s, the previous hottest decade.
NIWA has recorded the country's fluctuating temperatures since the mid-19th century.
Principal scientist James Renwick told Radio New Zealand's Summer Report the cause of the upward trend is due to a number of factors.
"What we see over New Zealand and globally is a combination of natural variations such as El Ninos and volcanic eruptions which play quite a role, but there's also the greenhouse gas-related trend."
Dr Renwick says the last decade was a tenth of a degree above the 1971 to 2000 average.
Federated Farmers president Don Nicolson says recent years of droughts mean many farmers have improved their use of available water, but he believes a more secure supply can be created.
"There are many examples of great water storage in New Zealand now, but enhanced water storage that covers a wider area is desired. We could do much, much more by future-proofing ourselves with water storage."
The Opuha dam in South Canterbury is a good example of how investment in water storage can reap dividends, he says.