A MetService spokesman said the thunderstorms would bring rain with intensities of up to 25mm per hour across the Clutha and Southland areas between 2pm and 9pm today.

"There is a risk some of these thunderstorms could become slow moving and may become severe, producing localised downpours of 25mm to 40mm per hour.

"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."

"Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain."

A Severe Thunderstorm Watch has been issued.

A Severe Thunderstorm Watch has been issued.

For information on preparing for and keeping safe during a storm, see the Civil Defence Get Ready website.

The southern warnings come as rain, humidity and warm temperatures are in store for much of the country today but better weather could be on the cards as we approach Christmas.

A warning is still in place today for the Coromandel Peninsula, which could have a deluge of up to 140mm of rain about the ranges,