If the longer nights, or change in the colour of some leaves wasn’t enough to tell you Autumn is coming, how about this wild swing in temperatures for Canterbury this week.

Starting late today, Wednesday, a westerly flow will develop over the lower South Island – it will turn more north west overnight tonight and on Thursday it will strengthen as a low pressure system near Fiordland pushes into high pressure over the North Island. Gales may even develop amongst the Southern Alps.

This will create a strong, hot, nor’wester for Canterbury.

Thursday’s highs push the mercury towards (and possibly over) 30 degrees across the Canterbury region.

Ashburton may hit 29 degrees on Thursday, with Christchurch and Timaru on 28 degrees.

But by Friday, Ashburton may be 16 degrees colder with a high of only 13 degrees expected.

Christchurch and Timaru look to tumble around 15 degrees by Friday.

Regions surrounding Canterbury, like Marlborough and Otago, will also have a warm Thursday and cooler Friday – but it appears Canterbury is most exposed to the ramping up of temperatures on Thursday – and the most exposed to the colder south to south east change blowing through on Friday.

Overnight lows behind the cold change will also be felt, with lows dropping to around 5 degrees for many parts of Canterbury.

If you’re a fan of the warm and settled – you’ll be pleased to know a large high moves back over the country this weekend bringing highs in Canterbury back to around the 20 degree mark.

– Friday’s temperature map shows the South Island much cooler than the North Island / WEATHERMAP

– WeatherWatch.co.nz