"It was the drought," he said.
"Then we got very strong winds in February, and then they got the rain at the wrong time."
He said the wine would be fine, but the volume would be "down significantly.
"In a way that's no bad thing, because it balances up the supply and demand."
Mr Riddiford said people needed to remember that wine producers were farmers, subject to the same problems as those dealing in dairy, beef, lamb or wool.
Palliser Estate was fortunate enough to have their own bores, but those without irrigation were hit harder.
"Like everything, you need water.
"Wine is pretty simple.
"If you taste it, and like it, you will buy it."
The reduced volume is likely to put a strain on UK outlets who favour the taste of New Zealand wine, according to hospitality supplier Beacon.
Beacon drinks buyer Mark Holness said the reduced harvest would mean a favourite summer drink would be harder to come by and more expensive to buy.
"There is concern that supplies of sauvignon blanc are also under strain following the poor harvest and we are working with our contacts and suppliers to identify the full extent of the problems," he said.
"In recent years, growers have also been moving away from the popular Marlborough region in New Zealand and so British drinkers might also notice a change in taste profile of the wine, which is something they may not be aware of yet."
It comes on top of a shortage in prosecco, another popular summer tipple in the UK.
