They said snow was melting in most places but low temperatures meant ice would form on the roads.
The Acting Road Policing Inspector, Glenn Nalder, says there had been some minor accidents but he was pleased with how well drivers were following advice to slow down and take care.
Most roads reopened on Tuesday after a snowfall that blanketed much of the country. However, there was black ice on state highways in inland Otago, and SH94 from Te Anau to Milford Sound was closed on Wednesday.
Chains were essential on all the mountain passes, and the following roads were closed to towing vehicles: SH6 (Haast Pass), SH73 (Arthur's Pass) and SH87 from Outram to Kyeburn.