The climate of the Comoro Islands, an archipelago in the Indian Ocean south of the Equator, is tropical, with a hot and rainy season from December to April, when the north-west monsoon prevails, and a relatively cool and dry season from May to November, when the south-east trade winds blow. The warmest period is from January to April, with an average daily temperature around 27 °C (81 °F), while the coolest months are July, August and September, when the average drops to around 23 °C (73 °F).
Here are the average temperatures in the capital, Moroni, located on the west coast of the island of Grande Comore.
Moroni - Average temperatures
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Min (°C)232323232120191819202223
Max (°C)303031303028282828293031
Min (°F)737373737068666466687273
Max (°F)868688868682828282848688

Of the three main islands that make up the archipelago, the two smaller ones (Mohéli and Anjouan) are occupied by hills in the interior, while the largest one, Grande Comore or Ngazidja, is home to a real mountain, Karthala volcano, 2,360 meters (7,743 feet) high. The slopes enhance cloud formation, which can lead to showers and thunderstorms, especially on the main island, which, in fact, is the rainiest. On Mount Karthala, up to 5,000 millimeters (195 inches) of rain fall per year, while Moroni, which is located on the windward side in the rainy season (that is, it is exposed to the north-west monsoon), receives 2,700 mm (106 in) of rain per year.
Here is the average precipitation in Moroni.
Moroni - Average precipitation
MonthJanFebMarAprMayJunJulAugSepOctNovDecYear
Prec.(mm)365295280315255265245150110951102202705
Prec.(in)14.411.61112.41010.49.65.94.33.74.38.7106.5
Days181618181212121011121216167

In Fomboni, on the island of Mohéli, total annual rainfall is 2,100 mm (83 in), while Ouani, on the island of Anjouan (also known as Nzwani), receives 1,800 mm (70 in) of rain per year. January is the rainiest month throughout the archipelago, with more than 300 mm (12 in) of rain along the coasts, while the driest month in Moroni is October, with 95 mm (3.7 in) of rain, which shows that showers and thunderstorms can occur quite frequently even in the dry season, at least on the main island. However, these rains, though intense, are short-lived, and they usually soon make room for the sun. On the smaller islands, during the dry season, showers are less frequent and less intense.
Here is the average precipitation in Fomboni.
Fomboni - Average precipitation
MonthJanFebMarAprMayJunJulAugSepOctNovDecYear
Prec.(mm)3302802452401801451551056090951952115
Prec.(in)13119.69.47.15.76.14.12.43.53.77.783.3
Days17151613121010746713130

Despite the rains, the Comoros suffer from a shortage of fresh water due to the absence of rivers.

Comoros

The amount of sunshine in the Comoros is not exceptional, nor scarce. The sun shines for a few hours a day even in the wettest months. The sunniest period is that of the trade winds, ie May-November, when, however, a bit of cloudiness can form, especially near the mountains. Here are the average sunshine hours per day in Moroni.
Moroni - Sunshine
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Hours667678877887

The sea in the Comoros is warm enough for swimming all year round: the water temperature ranges from 25 °C (77 °F) in August to 29 °C (84 °F) in the period from February to April.
Moroni - Sea temperature
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Temp (°C)292929292827262526262728
Temp (°F)848484848281797779798182

Tropical cyclones



The Comoros are located in the path of tropical cyclones, which can affect the islands from November to mid-May, though they are more likely from late December to mid-April.

Best Time



The best time to visit the Comoros and enjoy their yet uncrowded beaches, runs from June to October: it is the least sultry, the driest and sunniest period of the year, although some showers must still be put into account, especially on the main island. Here, given that the rains are still abundant in June and July, you can choose the period from August to October.

What to pack



In winter (June to August): bring light clothes, a sweatshirt for the evening, and a light scarf for the breeze.
When going to the reef, you can bring snorkeling equipment, including water shoes or rubber-soled shoes. To climb Mount Karthala, bring hiking boots, a fleece, a raincoat.
It's better for women to avoid shorts and miniskirts outside of tourist resorts.

In summer (December to February): bring tropics-friendly, loose-fitting clothing, light shirts and pants of natural fibers (cotton, linen) or synthetics that breathe, a light sweatshirt for the evening, and a light raincoat or umbrella.