A severe thunderstorm watch was put in place for parts of Canterbury and Otago on Sunday.
MetService issued the warning for the Canterbury plains, Canterbury high country, North Otago and Central Otago.
Some thunderstorms will be very slow moving and rainfall rates may range from 25 -40 millimetres per hour, giving rise to a moderate risk of severe thunderstorms. There may also be hail.
MetService said strong daytime heating together with a good moisture supply and wind convergence inland over mainly eastern parts of the South Island were combining to trigger deep convection.