The year in Louisiana, month by month
The figures are for the state's largest city, on the coast: 1,609 millimetres of rain a year over 115 days, a mean humidity of 76 per cent and mean temperatures running from 12.4 to 28.9 degrees. The scoring crosses rain, heat, humidity and hurricane season.
There are destinations where the question is when the rain stops. Here there is no answer: it rains in all twelve months, and in none of them does it drop below ninety millimetres.
So the right question is a different one: what kind of rain you will get, and with how many degrees and how much humidity on top.
01 Ninety-four millimetres in the driest month
The annual distribution is strikingly flat. The wettest month, June, leaves 193.5 millimetres; the driest, October, 94.0. Between maximum and minimum there is barely a factor of two, whereas in a Mediterranean climate that ratio can be twenty or thirty.
The annual total, 1,609 millimetres, is enormous for a city and is spread over 115 rainy days. That is, it rains on almost one day in three, every month, with no season off.
That has an immediate practical consequence: there is no month in which you can leave the rain jacket at home. What does exist is the month when the rain does not come with thirty-three degrees.
One thousand six hundred and nine millimetres and no month below ninety. Here you do not choose between rain and sun.
02 Two different rains in the same year
Winter rain and summer rain are nothing alike, even if the millimetres come out similar. From December to March the water arrives with fronts crossing the continent: whole grey days, fine persistent rain, and a temperature drop behind it.
From June to September the mechanism is different. Air loaded with gulf moisture heats over a plain at water level, rises and discharges in mid-afternoon convective storms: violent, short and local, with the sun back by dinner time.
For planning, that matters a great deal. In summer you can organise the day around the storm, because it is predictable; in winter you cannot dodge a front, but you do not need to, because rain bothers you less at twenty degrees than at thirty-three.
03 Summer is measured in humidity
July and August highs, 33.0 and 32.9 degrees, do not look extreme written down. The problem is not the number: it is that they come with a mean humidity of 79 per cent and night-time lows of 24.7 and 24.8 degrees.
With that combination the body cannot evaporate sweat efficiently, and the felt temperature shoots well above what the thermometer says. It is greenhouse heat, and it does not ease at night because the low stays at twenty-five.
The honest trade-off is that summer has its prize: the landscape is at its greenest, the swamps full and animal life at its most active. If you come for nature and can take the mugginess, it is not a bad deal.
04 From 1 June to 30 November
The Atlantic hurricane season officially runs from 1 June to 30 November, and its activity concentrates between late August and early October. This coast is one of the most exposed on the entire US seaboard.
It is worth sizing up what that means for a trip. The probability of a hurricane reaching you in any given week is low; what is not low is the disruption if it happens, because flights are cancelled, roads close and evacuations are sometimes ordered.
The reasonable advice is not to avoid the state for half the year, but to travel in those months with insurance, slack in the dates and no rigid plans. And, if you can choose freely, simply not to go at the September peak.
05 October, which is the answer
If the year has a clear winner, it is October. It is the driest month, with 94.0 millimetres over 7.1 days, and highs fall to 27.0 degrees with lows of 17.9. After four months of mugginess, that drop feels like changing country.
November comes right behind and in some respects improves on it: 98.3 millimetres over the same 7.1 days, highs of 21.8 degrees, and on the 30th hurricane season officially closes. It is the calendar's quietest month in every sense.
The other good window is spring, March and April, with 110.7 and 132.6 millimetres and highs of 22.4 and 25.8 degrees. It rains a little more than in autumn, but the countryside is in flower and the heat has not yet arrived.
06 How to choose the month
If you can choose without constraints, October and November. Less rain than any other month, highs of 21.8 to 27.0 degrees, manageable humidity and hurricane season fading or already closed.
If you prefer total green and a full swamp, March and April. And if your only window is summer, organise the days in reverse: early morning outside, afternoon under cover while the storm discharges, and another outing at sundown.
And one thing no month changes: bring footwear that can take a soaking and clothes that dry fast. With 115 rainy days a year and a mean humidity of 76 per cent, nothing here dries just by being left in the room.
The year's four stretches
From 104.9 to 131.6 millimetres a month, with highs of 16.9 to 19.1 degrees and lows down to 7.8. It rains with fronts, not storms, and humidity drops to 73 per cent.
From 110.7 to 143.3 millimetres, with highs of 22.4 to 29.6 degrees. May is the sunniest month, at 279 hours, but it already announces the heat to come.
671.3 millimetres across the four months, with highs of 31.2 to 33.0 degrees, lows up to 24.8 and 79 per cent humidity. It coincides with the bulk of hurricane season.
94.0 and 98.3 millimetres over 7.1 days each, the year's minimums, with highs of 27.0 and 21.8 degrees. Hurricane season ends on 30 November.
