Metservice has put the region under a heavy rain watch with heavy falls and thunderstorms possible from Friday evening.
The heavy rain watch covers the period from 7pm Friday night through till 7am Saturday morning and affects Nelson and Tasman north of Hope Saddle.
The forecast shows that a slow-moving convergence line may develop within the area, bringing with it heavy rain.
Thunderstorms are also possible on Friday evening.
Metservice says there is a moderate chance of the watch increasing to a warning.
