Hawke’s Bay was today bracing for the possibility of a storm threatening rain of up to 50mm an hour and thunder, lightning and hail with the potential to pulverise crops in the region.

While the twin cities were enjoying a sunny day during the morning and there had been no significant rain in most of the region in the past two days, Hawke’s Bay was under a MetService severe thunderstorm watch for 1pm-9pm, and a warning of heavy rain for the 30 hours to early evening on New Year’s Eve. The watch also applied to Wairarapa to the south and Gisborne to the north.

Significant hailstorms are a near-annual event in Hawke’s Bay, in particular in October-December, occasionally devastating the horticulture industry, sometimes with multimillion-dollar losses.

MetService said “conditions are right for severe weather” and meteorologist John Law said staff would be tracking developments throughout the day. Where “cells” were seen to be forming, MetService could issue precise thunderstorm and hail warnings at short notice and for short periods.

The thunderstorm watch warned of rain up to 50mm an hour, with a risk of flash flooding in low-lying areas such as streams, rivers and valleys, and also “large hail” with possible damage to crops, vehicles, and property. It also warned of hazardous driving conditions, including surface flooding, slips and poor visibility.

The heavy rain watch, covering the 30 hours from noon on Monday to 6pm on Tuesday, warned of periods of heavy rain, thunderstorms and localised downpours possible, mostly on Monday afternoon and evening.

Last week’s rain, heaviest in Northern Hawke’s Bay, was generally no more than 10mm an hour, providing some relief for some rural communities.

MetService said rain was expected to ease on Monday evening, but it warned periods of heavy rain with thunderstorms could again affect the area on Tuesday from pre-dawn to late afternoon.