Farmers in the southern half of the South Island have enjoyed relatively mild winter weather but were bracing for snow on Monday night.
MetService says snowfalls will cover farmland down to sea level in Southland, Clutha and Otago, and as low as 200 metres above sea level in Canterbury.
Strong winds and rain are also expected over the next 24 hours.
Andrew Morrison, who farms sheep near Gore, began lambing late last week and says the wind chill factor is the most concerning thing for farmers with newborns.
Mr Morrison says the cold snap is unusual for this time of year - though not unexpected - and fortunately stock and pasture are in good conditions due to a favourable winter.