Fernando de Noronha in the map

The climate of the archipelago of Fernando de Noronha, located near the northeast coast of Brazil, is tropical, hot all year round, with a dry season from August to January, and a rainy season from February to July. The archipelago is a UNESCO World Heritage Site.
Given the proximity to the Equator, temperatures are stable throughout the year, and are slightly higher from November to April, when highs are around 30 °C (86 °F), and slightly lower from May to October, when they are around 28/29 °C (82/84 °F). At night, the temperature almost never drops below 20 °C (68 °F).
Here are the average temperatures.
Fernando de N. - Average temperatures
Min (°C)252525242424242424242525
Max (°C)303030302929282829293030
Min (°F)777777757575757575757777
Max (°F)868686868484828284848686

In a typical year, about 1,400 millimeters (55 inches) of rain fall; the wettest period is from March to June, when the rains are equal to or higher than 200 mm (8 in) per month. Generally, the amount of rainfall in February and July is acceptable, but during some years it may be more abundant, reaching the level of the rainiest months.
Here is the average precipitation.
Fernando de N. - Average precipitation

The driest period, when it rarely rains, runs from September to December. October is historically the driest month, with fewer deviations from the norm, while in the other dry months, every once in a while an intense shower may occur.
The rainfall distribution in Fernando de Noronha is similar to that of cities located in the north-east of Brazil, such as Fortaleza and Natal.
Relative humidity is high throughout the year, and also in the dry season. However, fortunately, sea breezes give a bit of relief.

Sea in Fernando de Noronha

On average, the amount of sunshine is never scarce because the rains come in the form of downpours or thunderstorms, and usually do not last long, however, the sunniest period is the dry season.
Fernando de N. - Sunshine

The sea in the Fernando de Noronha Archipelago is warm enough to swim in all year round, as you can see in the following table.
Fernando de N. - Sea temperature
Temp (°C)282828292828272727272727
Temp (°F)828282848282818181818181

Best Time

The best time to visit the archipelago of Fernando de Noronha, either for exploring the islands by feet, or for sunbathing, swimming and diving, goes from August to January, since it is the driest of the year. Surfers will appreciate especially the period beginning in November and peaking in February and March, when waves are higher.