After a very cold start, thermometers have hit the 20s over parts of the mainland.

Overnight, temperatures took a big dive and approached the freezing mark but mild west to sou’ west winds in eastern and northern areas of the mainland have seen the mercury just sneak past 20.

Timaru is on 21 degrees with Blenheim, Christchurch and Ashburton close behind on 20.

Further south it’s a different story with cold westerlies in Invercargill with passing showers and just 11 degrees. A warmer day is likely for much of the south tomorrow with temperatures possibly in the high 20s in canterbury and Marlborough.