ripening grapes in the Marlborough sunshine

Marlborough’s climate is perfect for ripening grapes

Taking groups around the region on Na Clachan’s Marlborough wine tours, one of the most common questions is “what is it about Marlborough that makes the sauvignon blanc from here so distinctive?”

Great question.  Although there are a number of factors working together, one of the most important aspects is the Marlborough climate.  So in this blog I am going to concentrate mainly on the climate during the growing season.

Having lived in the north of Scotland for many years (now a long time ago, but some of those winters are etched into my memory, my description for the Marlborough climate in one word would simply be ‘brilliant’ but I guess a little more detail is required.

Blenheim is at a latitude of 41.5 degrees south – around the same latitude as Salt Lake City or Rome in the northern hemisphere.  The climate is cooler in the summer than those places because of the ocean close by – Cloudy Bay and the Cook Strait is only about 8km from Blenheim as the bellbird flies.

In the summer, December to March, the average daily maximum temperature is around 24 C.  That is the average though, we have many days where the temperature is creeping up to about 30 C.  32 C we would consider a very hot day.  But it is always a dry heat, so fairly comfortable.  Technically this makes us a cool climate for grape growing, although I tend to think it is plenty warm enough. However there is a bit of a sting in the tail.

Relaxing group

Planning to sit out all evening? Grab something warm

Picture this.  You have just arrived back at your accommodation after a glorious day’s wine touring with Na Clachan’s Marlborough wine tour.  You take a glass of chilled  Marlborough sauvignon blanc into the early evening sunshine with the temperature still around 28 C.  You plan to sit outside all evening, have a barbecue and wait for the southern cross to appear in the clear skies.  Wrong.  By the time the sun has gone down you have popped inside to find a sweater and an hour later you head inside for good because it is just a bit too cool.

That is the second great characteristic of our climate in the summer.  Cool nights.  The average minimum temperature in summer is around 11 C.  Warm days, cool nights.  Perfect for sauvignon blanc, chardonnay, pinot gris, pinot noir and riesling.   The plants are busy during the day, making the most of Marlborough’s sunshine and at night they lock those flavours away.  Not particularly well matched to the bigger heavy reds (syrah, malbec, cabernet sauvignon) which shut down at night and take too long to get going again the next day (I know how they feel!).

Marlborough sunset

Expect some stunning sunsets over the vineyards

Another important factor is the number of hours of sunshine, which I guess is related to the average annual rainfall.  Blenheim’s average sunshine hours total 2457 hours per year – equivalent to an average of 6.73 hours every day.  For those living in the UK, the equivalent figures for  London are 1500 per year, 4.10 per day.  So plenty of sunshine hours and warm, but not too hot temperatures enables a slow steady ripening and the retention of a good acid balance in the grapes.  Coupled with the high sunshine hours is the low rainfall, with an average annual total of 650mm (25.5 inches).  Vines do not like having wet canopies, it encourages a range of diseases, mainly moulds and mildews.  The low rainfall does mean we need to irrigate our vines, but we will talk about that in a later blog.  For now the low rainfall means reduced disease pressure.  I was listening to Hans Herzog, a boutique winemaker in the valley who grows organically, and he regards the low rainfall as essential in order to maintain organic practices.

The Wairau Valley is protected from rainfall on its southern, western and northern sides so it is in a rain shadow from these three directions.  One translation of the Maori name for the valley – Kei Puta te wairau – is ‘the place with a hole in the sky’.

The final climate effect is the relatively high UV levels in the valley.  NZ has about 40% higher UV levels than the UK.  On the down side this results in a high incidence of skin melanoma and as many an unsuspecting tourist will know very short burn times.  For the grapes the high UV leads to high levels of phenols in the skins of sauvignon blanc which may enhance the capsicum and gooseberry flavours so typical of Marlborough sauvignon blanc.

In summary, its complicated, but Marlborough sauvignon blanc is different from anywhere else in the world partly due to the climate

  • cool nights, warm days
  • low rainfall
  • high sunshine hours
  • high UV levels

Now you know the theory, why not jump aboard Na Clachan’s Marlborough wine tour and taste the difference for yourself.  You’ll also learn that climate is just part of the story.