Strewth mite, plenty of sound advice here already. Picturing OP arriving at Chch dressed in furry thongs & jandals, ready to tackle those -18°C
Matt, expect similar temps to what you have at home now. Bit wetter in the east, potentially much wetter in the west. Morning frosts should be all but finished. Unless it's another one like last year with temps approaching 30 inland some days. In which case non furry thongs, and jandals, might be in order.