The most heavily affected areas are expected to be Elsthorpe, Patangata, Omakere and central Hawke's Bay. Photo: 123RF
Hawke's Bay is currently under a severe thunderstorm warning.
MetService said very heavy rain, thunder, hail, strong wind gusts and possible tornadoes are moving east-south-east over Hastings.
The most heavily affected areas are expected to be Elsthorpe, Patangata, Omakere and central Hawke's Bay.
"Large hail can cause significant damage to crops, orchards, vines, glasshouses and vehicles, as well as make driving conditions hazardous," the forecaster warned on Friday afternoon.
"Rainfall of this intensity can cause surface and/or flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips.
"Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain."
People are advised to take shelter indoors, and anybody on the water should return to land.
MetService said it would deliver an update the Hawke's Bay situation at 9.30pm.
A heavy rain watch was also in place for Kāpiti Coast, Horowhenua, and the Tararua Range, as well as the Tasman District in the South Island.