The year in Alexandra, month by month
All the figures are Alexandra's, at 150 metres of altitude in the region's interior: 365.1 millimetres of rain a year over 66.2 days and 2,065.5 hours of sunshine. The scoring crosses three things: how much light there is, how warm it is by day and how cold it is by night.
New Zealand is a long, narrow country, surrounded by ocean on every side, and its climate answers to that shape: humid, temperate, without extremes, with mild winters and summers free of stifling heat. Almost the whole country fits that portrait. There is one place that does not.
In Alexandra, in the interior of Otago, the average high in January is 25.3 degrees and in July 8.8. Average lows run from 10.8 to −2.3. And as for extremes, the same station has recorded both 38.7 degrees and −11.8. That is not an island climate: it is the climate of a continental interior.
01 Figures that do not look like an island's
The figure that sums it up best is the rain: 365.1 millimetres a year, spread over 66.2 days. That is less than half what much of the country receives, and less than falls in many Mediterranean-climate areas. Alexandra's climate classification is oceanic bordering on cold semi-arid.
And there are records that reinforce the argument. Alexandra held for years the national record for lowest annual rainfall: 212 millimetres in 1964. In the same Otago interior, the Ranfurly station recorded, on 18 July 1903, the lowest temperature ever measured in New Zealand, −25.6 degrees.
The other weighty figure is the daily range. In January the difference between average high and average low is 14.5 degrees; in July, 11.1. A coastal place rarely exceeds seven or eight. Here day and night belong to almost different seasons.
02 How you dry out an archipelago
The first cause is a barrier. The Southern Alps cross the island from south-west to north-east and block the moist westerlies, which dump their water on the seaward flank. What reaches the far side arrives dry. Central Otago is on the lee side, in full rain shadow.
The second is distance. In a country where almost nowhere is far from the coast, this interior is the exception: it is the area furthest from the sea in all New Zealand, and Alexandra is among the country's most inland towns. The ocean, which everywhere else softens both cold and heat, here does not arrive in time.
The third is the shape of the ground, which we already know: closed basins ringed by ranges. Cold air is denser, so on clear nights it pools in the valley floor and stays there. Historically, low-lying areas have recorded between 50 and 100 frost days a year.
03 Eighty-four hours of sunshine in June
Otago's winter has two distinct problems and they are worth separating. The first is the cold: July gives average highs of 8.8 degrees and lows of −2.3, with a record of −11.7 degrees at the Alexandra station itself. Those figures are ordinary in central Europe and very rare in New Zealand.
The second is light, and it is the one that weighs most on a trip. June totals 84.0 hours of sunshine for the whole month: under three hours a day. July, 87.0. Against January's 253.1, the difference is three to one. You are at around 45 degrees south, so the days are short as well.
August marks the turn. Rain hits its annual low, 15.4 millimetres over 4.2 days, and sunshine jumps to 135.6 hours, more than 50 % above July. Lows are still below zero, but the month is no longer dark.
04 And thirty-eight degrees in January
Summer flips the portrait entirely. January and February give average highs of 25.3 and 25.2 degrees, with 253.1 and 216.6 hours of sunshine. The station's absolute record is 38.7 degrees, reached in both January and February. By New Zealand standards that is unusual heat.
But the heat does not stay for the night. In January the average low is 10.8 degrees: fourteen and a half degrees below the high. That contrast is the signature of a continental climate and it has one very concrete practical consequence: whatever the day is like, a warm layer goes in the pack.
The same mechanism explains something that surprises anyone who knows the rest of the country: here autumn shows. The poplars and fruit trees of the valley change colour in March and April with an intensity a maritime climate does not produce, because it takes cold nights and dry days.
The year's four stretches
From 34.5 to 46.9 millimetres a month over about six days, with 216.6 to 253.1 hours of sunshine and highs of 23.8 to 25.3 degrees. This is the continental summer: very dry days, nights down to 10 degrees and records reaching 38.7.
From 31.2 to 22.0 and 34.3 millimetres, with sunshine falling from 181.2 to 104.3 hours. Highs go from 22.5 to 13.5 degrees and lows from 7.5 to 1.4. March and April are the best months for walking with enough light.
30.9, 25.2 and 15.4 millimetres, and only 84.0, 87.0 and 135.6 hours of sunshine. July gives average highs of 8.8 degrees and lows of −2.3. The interior of Otago is the only part of New Zealand where winter behaves like this.
21.3, 29.6 and 32.7 millimetres, with sunshine climbing from 169.6 to 236.4 hours. Highs go from 16.5 to 21.3 degrees, but lows are still 2.2 and 4.6 in September and October: pleasant days and cold early mornings.
05 It rains in summer, not in winter
There is one more twist in the table. Against what you might expect from a climate with hard winters, the wettest month of the year is January, with 46.9 millimetres, and the driest is August, with 15.4. In other words: the peak of rain coincides with the peak of heat and light.
The amount, in any case, is so small that it barely changes a plan. Forty-seven millimetres over six days is an occasional afternoon storm, not a rainy season. The month with the most days of precipitation is May, with 6.8, and the fewest, August, with 4.2: between the best and worst month there are two and a half days of difference.
The useful conclusion is that in Otago rain is not the deciding variable. What decides is light, running from 84 to 253 hours a month, and night temperature, running from −2.3 to 10.8 degrees. Choose by those two and you will get it right.
06 How to choose the month
If you can go only once, go in March: 31.2 millimetres over 5.2 days, 181.2 hours of sunshine, average highs of 22.5 degrees and nights of 7.5. It has light to spare, the strong summer heat has passed and it coincides with the leaf change in the valley.
If you are after heat and long days, January and February are unbeatable, with 253.1 and 216.6 hours of sunshine and highs above 25 degrees. Reckon with the fact that they are also the two busiest months, and that the sun bites hard at this latitude and in air this dry.
And if you go in winter, go for what winter does rather than in spite of it: fog settled on the basin floors, frost over the tussock, snow on the ranges. But count the hours before you book. June gives 84.0 hours of sunshine for the whole month, and on that budget of light a day out runs short very quickly.
