Weather Predictions for Summer 2018 - 2019

One of the most talked about topics on the track, what’s the weather going to do? When is it going to rain? When will the rain stop? With the track becoming so busy, which means you have to book months ahead to get a bed. The questions then are what’s the best time of year to walk the Routeburn? Is it a matter of luck if you have good or bad weather? Is there any way to predict what the weather will be in a month or even 6 months from now? Many questions, but not many answers. Certainly, the weather is constantly changing and it seems there is no way to predict what it will do tomorrow let alone next week. However, like many things in life, the weather also has its cycles and patterns.

Please note that the following predictions were based on statistics mixed with weather cycles. There is no guarantee that the weather will follow these patterns.

With the above average temperatures during the summer becoming more frequent, the weather patterns are changing. Usually, when a rain front hits NZ it is at the lower to mid-south island region. With the warmer weather, these similar fronts are now hitting NZ mid to upper south island region. The warmer sea temp also means there is more moisture being sucked up into these fronts. Which means heavier rainfalls. We could see October –January have below average rainfall and February – May above average rainfall.

It seems easier to predict when the weather is wet and wild then fine and sunny.

So the following are probabilities of when there is a high chance of wet weather.
October 2018
Rainy days - 2, 3,    9, 10,    15, 16,    24, 25, 26,    29
Wild weather days with gale force Westerly Winds and rain – 9, 24
Cold Southerly winds (possible snow to low levels)– 16
Clear Blue Sky days – 17, 18

November 2018
Rainy days - 5,    11, 12,    16, 20,    25, 26
Wild weather days with gale force Westerly Winds and rain – 5, 20
Cold Southerly winds (possible snow to low levels)– 12
Clear Blue Sky days – 13, 14

December 2018
Rainy days - 3,    9, 10,    16, 17,    24, 25,    29, 30
Wild weather days with gale force Westerly Winds and rain – 3, 17, 30
Cold Southerly winds (possible snow to low levels)– 10
Clear Blue Sky days – 11, 12

January 2019
Rainy days - 5, 6,    13, 14,    20, 21, 22, 23,    26, 27
Wild weather days with gale force Westerly Winds and rain – 14, 26
Cold Southerly winds – 6
Clear Blue Sky days – 7, 8

February 2019
Rainy days - 1, 2,  10, 16,    20, 21, 22, 23
Wild weather days with gale force Westerly Winds and rain – 10, 23
Cold Southerly winds – 2
Clear Blue Sky days – 3, 4

March 2019
Rainy days - 8, 9,    15,    21, 22, 23,    28, 29
Wild weather days with gale force Westerly Winds and rain – 9, 22
Cold Southerly winds (possible snow to low levels)– 2, 29
Clear Blue Sky days – 3, 4, 30, 31

April 2019
Rainy days - 5, 12,    18, 19, 20, 21,    24, 25
Wild weather days with gale force Westerly Winds and rain – 5, 19
Cold Southerly winds (possible snow to low levels)– 25
Clear Blue Sky days –26, 27

May 2019
Rainy days - 3, 4,    8,    15, 16,    21, 22, 23,    27, 30
Wild weather days with gale force Westerly Winds and rain – 3, 16, 30
Cold Southerly winds (possible snow to low levels)– 23
Clear Blue Sky days – 24, 25

There are also approx. 2 week cycles where the rain is not as heavy than other 2 week cycles.
Here is a selection of dates where it can still rain but in general it will be less rain than the two weeks either side.
Expect rain at either end of these dates.
October 23 - November 5
November 20 – December 2
December 17 – December 30
January 13 – January 26
February 10 – February 22
March 9 – March 22
April 5 – April 18
May 2 – May 15
May 30 - June 12

So it’s going to rain at sometime. So how about what time of day?
During these periods it is likely that any rain will fall heaviest during the night time.
On rainy nights expect it still to be raining in the morning, but clearing as the day goes on.
October 9 – November 17
December 8 – December 16
January 6 – January 14
February 5 – February 13
March 7 – March 14
April 5 – April 13
May 4 – May 12

For those that love to get out into a good storm with plenty of Lightning and Thunder.
Any rain during these periods have a very high probability of Thunderstorms/Lightning
October 25 – November 1
November 23 – November 30
December 23 - December 29
January 21 – January 28
February 20 – February 27
March 21 – March 28
April 19 – April 27
May 19 – May 27

For Stargazing the best nights if the skies are clear are between:
October 4 – 14
November 3 – 13
December 2 – 12
January 1 – 11
February 1 – 10
March 2 – 12
April 1 – 10
May 1 - 10