MetService is warning parts of the South Island could be in for severe thunderstorms and "damaging" hail as a cold trough moves eastwards over the island on Thursday.
The trough is expected to cause thunderstorms in eastern South Island areas. The main risk areas are mid-Canterbury to Dunedin and also around the Kaikoura Ranges in the afternoon and early evening on Thursday.
"Most of the thunderstorm activity is expected in the afternoon and early evening, but there is a low risk of one or two developing about eastern parts of inland Southland, Otago and South Canterbury from late morning," MetService said.
The forecaster said these thunderstorms will produce localised heavy rain of 10-20 mm/h and hail of 10-20mm diameter.
"There is also a low risk that one or two of the thunderstorms could be severe about North Otago and South Canterbury (mainly near the coast) with larger damaging hail in excess of 20 mm diameter.
"If large hail does occur, it could cause damage to crops and orchards, as well as cars and glass-houses, and make driving conditions hazardous."
North Island
It's not just the South Island at risk - Metservice said parts of the North Island could be in for thunderstorms and hail due to a combination of daytime heating, a southeast wind change and cool temperatures.
The forecaster said these conditions will allow cloud buildup, which will produce scattered showers around the central North Island on Wednesday afternoon and evening.
"There is a low risk of isolated afternoon and evening thunderstorms about the central North Island mountains and ranges (north of the Napier-Taihape Rd), and a low risk of isolated evening thunderstorms about parts of Bay of Plenty, Rotorua, Taupō and South Waikato," MetService said.
"If any thunderstorms do develop, they will produce localised heavy rain."
