Overnight downpours have led to some Christchurch roads being closed, and there are warnings of more rain to come.
Roads affected include Bellbrook Cres, Emmett St and Orcades St.
MetService is warning areas north of Fairlie, along with coastal regions and the plains to brace for as much as 60mm of rain through to tonight.
Trampers in the area to be on the lookout for rising rivers, floods and slips and the foothills from Porters Pass southward are expected to be hit particularly hard.
Snow is also expected to reach the same areas above 500m throughout the day, with up to 35cm possible at Porters Pass and up to 15cm further north.
"Heavy snow is likely to cause disruption to transport and place stress on livestock," forecaster Heath Gullery said.
Meanwhile, lightning strikes nearly hit the 10,000 mark overnight as thunderstorms swept across the country.
More than 100 strikes were recorded in Auckland yesterday evening, one video showing bolts of lightning hitting the Sky Tower, while thunder shook people's houses.
