MetService has issued a severe thunderstorm watch for the lower South Island this afternoon.
The forecaster said the combination of a warm, humid afternoon and light winds was expected to produce scattered thunderstorms about inland South Canterbury (south of about Twizel), inland eastern Otago, Southland and southern Fiordland.
MetService said the watch affected people in North Otago, Central Otago, Dunedin, Clutha, Southland, Fiordland and the Canterbury High Country until 9pm.
Between about 2pm and 9pm, a few of these thunderstorms could be severe, with localised downpours of 20-40mm per hour.
More thunderstorms were forecast in these areas on Saturday afternoon and evening.
Earlier, a heavy rain warning was issued for the Westland ranges south of Otira from today until Saturday morning, before easing. MetService said in the 24 hours from 9am today, between 100mm to 120mm of rain was expected.
The intense rain could 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 would be hazardous, with surface flooding and poor visibility in heavy rain.
Showers were forecast for Dunedin, Queenstown, Wanaka, Alexandra, Oamaru and Invercargill today, but it would still be warm with temperatures in the early 20s.
People were advised to keep up to date with the latest forecasts.
