Moroni month by month — at a glance
Hover each month for the summary. Click to pin it.
01 There is no dry season
Key moments at a glance
97 mm over 12 days. Almost four times less water than January.
108 mm, 28.1 °C by day and 19 °C by night, humidity at 70%.
150 mm, 65% humidity and the year's lowest mean low: 18.4 °C.
18 rain days and 79% humidity. The month to avoid.
The distribution has a clear shape. From December to April the city receives between 279 and 364 millimetres a month over 16 to 18 rain days. From May to July it drops to 244–266 millimetres but over only 12 days: the water concentrates into shorter downpours. And from August to November it falls to 97–150 millimetres.
January: 364 millimetres. October: 97. The same city with almost four times more water on it, and neither month is dry.
02 August, September, October
Those are the three months, and there is no arguing about it. October is the driest in quantity, at 97 millimetres; September has the fewest rain days along with August — eleven and ten — and totals 108 millimetres; August is the coolest of the year, with a mean high of 27.7 degrees and a mean low of 18.4.
If you have to pick just one, pick September. It combines October's low quantity with August's cool nights and a humidity of 70%, well under January's 79%. It is the point at which this climate is most bearable for someone not used to it.
03 Humidity decides more than rain
Temperature barely takes part: the mean high runs from 27.7 degrees in July and August to 30.8 in March and December; the mean low from 18.4 in August to 23.4 in January. Five degrees above and five below across twelve months. It is never cold and never dangerously hot — the absolute record is 36 degrees.
What does move is relative humidity: from 65% in July and August to 79% in January. Fourteen points, in a place where the temperature is always around thirty degrees. That is the real difference between a pleasant day and a sticky one, and it is the figure to look at when choosing a month.
.jpg?width=1200)
04 What it means on the ground
It is worth translating the numbers into decisions. With 167 rain days a year, the probability of rain during your trip is effectively one hundred per cent, whenever you come. What changes between October and January is not whether it will rain, but how often and for how long.
That has two practical consequences. First, that there is no point planning the day around the forecast: you go out, it rains, you wait twenty minutes and carry on. Second, that if your trip includes climbing the volcano — and it should — the month matters far more than it does for walking the city: on the slope the cloud closes in and the volcanic ground turns slippery.
And one last thing worth knowing before booking. These islands are exposed to south-west Indian Ocean tropical cyclones: Cyclone Elinah, in the 1982–83 season, made landfall on the archipelago and caused significant damage to infrastructure. It is an infrequent but real risk, and one more reason to check your government's official advisory before fixing dates in the wettest months.
