Nuku'alofa month by month, at a glance
Hover each month for the summary. Click to pin it.
Nuku'alofa lies at 21 degrees south, far enough from the equator for something to happen here that happens in almost no other tropical Pacific capital: the year has two different temperatures. Between February and August the average high falls from 29.9 to 24.8 degrees and the average low from 23.7 to 18.2. The city's cold record is 10 degrees, in July.
And that cool half coincides, almost to the day, with the only window in the year when the law allows you to get into the water with a humpback whale.
01 Five degrees you actually feel
The full temperature range is about five degrees in the highs and five and a half in the lows. It does not sound like much on paper, but it is the difference between sleeping with a fan and without one, and between walking around town at midday or waiting for the sun to drop.
Humidity follows the same movement, though more discreetly: it falls from 79 per cent in March to 73-75 per cent from July to December. The mugginess loosens exactly when the temperature drops.
The sea does the same, and it is worth knowing before you pack: from the 27 or 27.5 degrees of the southern summer it drops to 23.5 in August and September. You can still swim perfectly well, but for several hours in the water in the best whale months a thin wetsuit stops being a luxury.
Key moments at a glance
122 mm over 13 days, highs of 25.3 and whales still in the water.
95 mm and lows of 18.1; on the 1st the whale-swim season opens.
210 mm, highs of 29.9 and the middle of cyclone season.
Little rain, 123 mm, but cyclone formation starts.
02 Rain matters less than it looks
The city gets 1,721 millimetres a year spread over 180 rain days. Which is to say: it rains one day in two, in any month. With a distribution like that, choosing by the rain gauge does not get you far.
Even so, the extremes exist. June and July are the driest months, at 95 millimetres each; February and March the wettest, at 210 and 206 over 19 rain days each. Between the driest and the wettest month there is a little over double, not the triple or quadruple of other Pacific destinations.
The most useful figure in the table is not the water but the days: October has only 11 rain days, the year's minimum, and August and September have 13. January, February and March climb to 17 and 19. That is a difference that actually changes a trip.
03 The other half of the calendar
Cyclones form here between November and mid-May, and are most likely between late December and early April. That window overlaps almost exactly with the warm, wet block, so the two reasons to avoid those months point the same way.
It is not a theoretical risk. In February 2018 Cyclone Gita destroyed the parliament building in the capital itself. Before that came Waka in December 2001 and Heta in January 2004, and all of them fall inside the same stretch of the calendar.
The practical consequence is the usual one and worth applying: in those months, insurance that covers cancellations, no stringing flights and boats together without slack, and an expectation that a warning can erase two consecutive days of the itinerary in a country that moves by boat.
04 A window with a date in the rulebook
Humpbacks come up every year to breed in these warm waters. Around Tongatapu they show from mid-June to the end of October, and the regulations set the season in which swimming with them is permitted between 1 July and 30 October. Outside those dates you do not get in the water, however many whales there are.
Inside the window the best months are August and September. Only accredited operators may approach within 300 metres, and only those additionally licensed to swim may put anyone in the water; once in, you must keep at least five metres from the animal.
That is why the calendar reads backwards here compared with other places: you are not looking for the month with least water, you are looking for the month that is both outside cyclone season and inside whale season. That overlap leaves July, August, September and October, and of those four, September is the roundest.
05 What to pack, and in short
Light quick-drying clothes and, this time yes, a thin long-sleeved layer: July and August bring 18-degree nights and on the boat, wet and in the wind, you will want it. A thin rain shell, footwear that grips on coral rock, high-factor sun protection and a dry bag. If you are going for whales, a thin two or three millimetre wetsuit.
In short: July to October, with September at the head and August close behind. June works well for weather but falls outside the official swimming season. From December to April it is hotter, it rains almost twice as much and cyclone season is open.
The month is not decided here by the rain, which is spread through the whole year. It is decided by two dates: when cyclone season closes and when whale season opens.
