The year in Krabi, month by month
The figures are monthly averages for Krabi over the 1981–2010 series: 2,000 millimetres of rain a year over 166 days, with 5.4 hours of sun a day on average. The scoring crosses rain, rainy days, sunshine and sea state; temperature hardly counts because it hardly moves.
Almost everything written about when to go to the Andaman coast boils down to one sentence: the southwest monsoon runs from May to October. The sentence is correct and misleading, because it invites you to think October is the month when things are winding down.
It is the other way round. October is the worst of the six, and the one after it is not clean either.
01 October is the monsoon's last month and the wettest
The year's figures leave no doubt. May gives 170 millimetres, June 195, July 200, August 265, September 275 and October 325. The curve rises continuously through the six months and is cut off abruptly at the end.
The same happens with rainy days: 16, 16, 18, 18, 19 and 22. In October it rains seven days out of ten, the highest frequency on the calendar.
The reason is that the rainfall maximum does not coincide with the monsoon's energy maximum, but with the moment the system retreats and turns unstable. The closing month is the one that dumps the most water.
Three hundred and twenty-five millimetres over twenty-two days: the wettest month of the year is the last of the rainy season, not the middle one.
02 And November, no longer monsoon, keeps raining
The calendar's second trap comes right after. November falls outside the definition of the southwest monsoon and appears in many guides as the start of the high season, but it collects 180 millimetres over 18 days.
That is more water than May, June or July, meaning more than three of the six officially wet months. And it is the same 18 rainy days as July and August.
The real cut comes in December, when rain drops from 180 to 70 millimetres and rainy days from 18 to 10 in a single step. That is the month when the dry season genuinely begins, not November.
03 Sunshine drops to less than half
There is one variable that describes the travel experience better than millimetres, and it is sunshine. In February 7.5 hours of sun a day are recorded. In October, 3.5.
Less than half. And November, the month many take as good, stays at 4.5 hours, still well below December's and January's 6.
The difference shows in concrete things: the colour of the water, which without direct sun loses its turquoise entirely; how your body feels on coming out of the sea; and the reliability of any plan depending on light. In the wet season it does not rain all day, but the sky is closed almost always.
04 The thermometer barely takes part
While rainfall multiplies by ten between February and October, temperature barely notices. The highest average maximum is March's, at 34.3 degrees, and the lowest November's, at 31.1: three point two degrees of range across the whole year.
The minimum is even steadier: it goes from 21.6 degrees in January to 23.7 in May, two point one degrees. That is, Krabi's night is practically the same all twelve months.
And there is a relationship worth being clear about: the hottest month, March, is also one of the dry ones, and the coolest, November, is one of the wet ones. Here the rain does not arrive to put out an unbearable heat; it arrives and takes off three degrees you hardly needed shifting.
05 The sea is at thirty degrees all year
Water temperature completes the picture and is the steadiest figure of all. The Andaman Sea moves between 28 degrees in January and 30 in April, May and June. It never drops below 28.
That means swimming never enters the equation of when to come. What does enter is the state of the sea: in the wet season swell increases and trips to the islands depend on the day and, in some cases, are cancelled.
The tide, by contrast, has no season. The average range at Ao Nang is around 2.1 metres, with maxima of some 3.3 at springs and minima of some 0.7 at neaps, and that conditions the timetable of almost any boat trip all twelve months.
06 How to choose the month
If you can choose without constraints, February and March. February gives the rainfall minimum with the sunshine maximum — 45 millimetres and 7.5 hours — and March adds the heat, with highs of 34.3 degrees, in exchange for rising to 100 millimetres over 9 days.
If you are after price, the May to July stretch is the most reasonable of the wet season: 170 to 200 millimetres over 16 to 18 days, with 5 hours of sun and highs of 31.5 to 32.9 degrees. It rains almost every day, but in showers that leave usable gaps.
And if the trip falls in September, October or November, adjust expectations before leaving: between them they add up to 780 millimetres over 59 rainy days, with sun between 3.5 and 5 hours a day. It is not a bad trip, but it is not a beach trip.
The year's four stretches
From 30 to 100 millimetres a month over 5 to 10 days, with 6 to 7.5 hours of sun daily. Highs of 31.4 to 34.3 degrees and sea between 28 and 29. These are the four months when the calendar works without conditions.
145 millimetres over 12 days with highs of 34.1 degrees and the sea at 30, its annual maximum. It is still a good time, but humidity and afternoon storms already show.
From 170 to 200 millimetres over 16 to 18 days, with 5 hours of sun. It rains almost daily, but in showers, and the maximum falls to 31.5 to 32.9 degrees. It is the cheap half of the year.
From 180 to 325 millimetres a month over 18 to 22 days, with sun between 3.5 and 5 hours. October holds the maximum and November, already out of the monsoon, still leaves 180 millimetres.
