São Tomé, the capital of São Tomé and Príncipe, sits on the northeastern coast of the volcanic island of São Tomé in the Gulf of Guinea, almost exactly on the equator at approximately 0.34°N, 6.73°E. It has a tropical climate — hot and humid — moderated by the ocean, with a long rainy season and a distinctive cool dry season.

There is no summer in the temperate sense: temperatures barely change, with daytime highs around 29–30°C and warm, humid nights near 22–23°C. The rainy season runs from October to May, bringing frequent heavy afternoon downpours and thunderstorms, with abundant cloud and high humidity across the volcanic island.

There is no true winter, but the cool dry season from June to September — known as the gravana — brings slightly cooler temperatures, little rain and lower humidity. Counter-intuitively, this dry stretch is often the cloudiest and greyest of the year, with overcast skies persisting despite the absence of rain, as cool Atlantic air drifts over the island.

São Tomé receives on the order of 900–1,000 mm of rain a year in the capital, concentrated in the rainy season from October to May, while June to September is markedly dry; the island's mountainous, windward southwest receives many times as much — several metres a year. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

São Tomé's volcanic peaks create one of the sharpest rainfall gradients anywhere: the sheltered northeastern coast where the capital sits is relatively dry, while the windward southwestern slopes, drenched by the monsoon, receive several metres of rain a year and are cloaked in dense rainforest.

To follow any single measurement in Sao Tome more closely, use our live instruments: the online barometer for atmospheric pressure, the thermometer for temperature, the hygrometer for humidity, the anemometer for wind speed, the wind vane for wind direction, and the rain gauge for rainfall.