The watch has been issued for 11 hours from 2pm today until 1am tomorrow for Canterbury, and eight hours from 11am to 7pm today for Fiordland, Stewart Island, and inland Southland and Otago.
MetService is encouraging those in the area to stay up to date with forecasts.
Weather watches are used when severe weather is possible, but not imminent or certain, MetService said.
“When a watch is in place, stay alert and keep an eye on your local forecast for updates.”
A weather warning is issued when forecasters are confident weather of a significant impact will occur.