The year in Arusha, at 1,400 metres
The figures are those of Arusha city, in the middle of the region. The annual total is 1,180 millimetres and the mean temperature 17 degrees. The scoring depends almost entirely on rainfall: highs move between 20 and 28 degrees across the whole year.
Almost all the information circulating about when to visit this region boils down to one sentence: go in the dry season, June to October. It is correct advice and it is half the answer.
The year here does not run on two seasons but on four, because the rainfall has two separate peaks rather than one. And that means there are two dry periods, not one, and the second is practically empty of visitors.
01 The year has four seasons, not two
The millimetres month by month draw it without ambiguity: 50 in January, 80, 170, 360, 210, 30, 10, 10, 20, 30, 110 and 100 in December. There are two rises and two falls, not one of each.
Each stretch has its Swahili name and they are worth knowing, because they are the ones used on the ground. The masika is the long wet season, March to May. The kiangazi is the dry one, June to October. And the vuli is the short wet season, November and December.
The fourth stretch does not have an equally well-known name and it is the one that matters here: the two months left between the end of the vuli and the start of the masika. January and February, with 50 and 80 millimetres, are a dry period in their own right.
02 April against the five dry months
To calibrate the difference between the stretches there is one comparison that works better than any explanation. April leaves 360 millimetres of rain. The five months of the dry season — June, July, August, September and October — add up to 100 between them.
Which is to say: in a single month more than three and a half times the water of almost half a year falls. And it is not a month of afternoon storms as in other high-altitude places: it is the heart of a monsoonal regime, with saturated ground and dirt tracks at their worst.
There is also a local nuance worth keeping in mind. The masika is more reliable here than in the surrounding areas because of the influence of Mount Meru, whose 4,562-metre mass alters the rainfall regime. Which is to say: in April, in Arusha, it rains more and more dependably.
03 The long dry season
The June to October block is the one everybody knows, and rightly so. Its figures are 30, 10, 10, 20 and 30 millimetres. July and August, with ten each, are the driest months of the year.
What gets told least about these months is that they are also the coolest. July has average highs of 20 degrees — the lowest in the calendar — and lows drop to 8 in June, August and September. At 1,400 metres and at this latitude, July mornings are genuinely cold.
That cold is the price of the sky. Anyone booking July or August expecting tropical heat will need more clothing than they packed, especially if sleeping above the city's altitude.
04 The window hardly anyone uses
And now the interesting stretch. January and February leave 50 and 80 millimetres, more than July but far less than any month of the masika or the vuli. They are, in practice, a second dry period of two months.
And they have one important difference from July and August: they are the two warmest months of the year, with average highs of 28 degrees, and the landscape is still green because it has just rained in November and December. It is countryside with recent water and clear skies.
The honest trade-off is twofold. First, that January and February are less dry than July and August, so there is a higher chance of a shower. And second, that the window is narrow: by the second half of February the masika is already showing and in March the rain doubles.
05 And the temperature, almost flat
One detail that greatly simplifies packing: the temperature barely moves. Average highs run from 20 degrees in July to 28 in January and February, and lows from 8 to 13. The annual mean is 17 degrees.
The reason is altitude: the city sits at 1,400 metres and the region runs from 900 to 1,600. A few degrees from the equator, those metres turn a tropical climate into a mild, stable highland one.
Which is why the question here is never how hot it will be, but whether the ground will be passable. In a place where getting around depends on dirt tracks, rain is not an aesthetic nuisance: it is what decides where you can get to.
The year's four stretches
30, 10, 10, 20 and 30 millimetres: a hundred across all five months. It is also the coolest stretch, with highs of 20 degrees in July and lows of 8. Passable ground, clean skies and genuinely cold mornings.
50 and 80 millimetres between the short and the long rains, with highs of 28 degrees, the year's peak. The countryside is still green from the vuli and the sky is clear. Less dry than July, but much milder.
110 and 100 millimetres with highs of 27 degrees. A brief, irregular wet season: it rains, but on a scale that has nothing to do with April. The landscape goes from straw to green in weeks.
170, 360 and 210 millimetres. April alone drops more water than the five dry months combined, and here the masika is more reliable than in neighbouring areas because of Meru's influence. This is the stretch to avoid.
06 How to choose the month
If the priority is dry ground with no surprises, the answer is July or August, with 10 millimetres each. It is the calendar's absolute minimum and there is nothing to argue about. In exchange, expect mornings of 8 degrees.
If temperature and the look of the countryside also matter, January is the year's best bet outside the well-known block: 50 millimetres, highs of 28 degrees and a landscape that has just taken November and December's water.
And the rule with no nuance: do not book April. Three hundred and sixty millimetres in one month, in a region where getting around depends on dirt tracks, is not a drawback that anything makes up for. May, with 210, is not a good idea either.
