This was concerning because if the water did not drain away quickly the vines would soak up the moisture, and the berries would burst, Mr Shepherd said.
"The week coming will be telling times, because if the berries burst we could end up getting sour rot. The fruit may just rot on the vine yet, we don't know, we just have to wait and see.
"We've just got to hope everything dries out properly, and it drains away."
It appears Thursday's heavy rain was isolated to areas around Napier, which means the
rest of the region's wine industry has not been badly affected.
Hawke's Bay Winegrowers Association deputy chair Xan Harding said it appeared the Esk growers were the worst hit, with no significant impact across the wider wine sector as only 60ml to 90ml of rain fell across the rest of the Heretaunga Plains.
"It's come through very quickly and it's cool, and now it's very windy so it's drying up. Out having a look today I haven't really seen any significant effect of it. It may bring forward the harvesting of a few crops early this week."
As Hawke's Bay's vintage is spread, starting late February and carrying on into April, Mr Harding said there were only a few varieties close to ripening.
There was concern about the impacts of Cyclone Hola. There was likely to be more rain, and warmth which was "less than ideal", but they hoped it would pass through the region quickly so everything could be back on track early next week.