Climate and monthly weather forecast
Tristan da Cunha, Saint Helena, Ascension and Tristan da Cunha

Tristan da Cunha claims a presence in the South Atlantic Ocean, served by a climate classified as Marine west coast with warm summers, under the Köppen climate classification. Known as Cfb, this climate type bestows this remote island territory with consistently mild and humid conditions throughout the year. As such, it exhibits a relatively small temperature fluctuation between the colder and warmer months.

Throughout the year, the high temperatures fluctuate between 14°C (57.2°F) and 21°C (69.8°F), while the lows can range from 10°C (50°F) to 17°C (62.6°F). Within these confines, the mercury shows a modest dip during the winter months, with highs reaching 14°C (57.2°F) and the lows dwelling around 10°C (50°F). Contrarily, the summers are a taste of mild warmth with high temperatures peaking at 21°C (69.8°F).

Adding depth to the weather portrait is the precipitation patterns, which remain fairly consistent throughout the year. Rainfall, marked in millimeters, ranges from 93mm (3.66") in the drier month to 175mm (6.89") during the wettest period. Correspondingly, the number of rainfall days sees a steady increases from 18 days at the beginning of the year, peaking at 26 days in August before retreating.

While the cloud cover persists, Tristan da Cunha also plays host to a fair amount of sunshine. Sunshine hours per day vary, with an average low of 3.3 hours during the winter months, and reaching up to 5.1 hours in spring. The UV index, an important measure of sun intensity, exhibits a similar pattern, oscillating from a low of 2 in winter to a high of 12 in summer.

Adding to Tristan da Cunha's unique weather attributes is the sea temperature, ranging from 13°C (55.4°F) to 18°C (64.4°F) over the course of the year, and the daylight hours, doing a dance between 9.6 hours in winter to a brilliant 14.7 hours in summer.

Pairing the temperature and rainfall trends, it appears that the best time to visit Tristan da Cunha would be in the period from April to June. During this time, temperatures maintain a comfortable range from 18°C (64.4°F) to 15°C (59°F), while the rainfall precipitation tends to be moderate. The daylight hours fall between 11.1 hours to 9.6 hours, providing a generous portion of the day for outdoor activities.

Narrowing down to the less favorable period for visitation, August emerges as the worst time to make a trip. This is when the island contends with the highest precipitation of 175mm (6.89"), spreading over 26 days. The daylight hours are also at their lowest range, limited to a mere 10.7 hours. Coupled with the lowest sea temperature at 13°C (55.4°F), this presents a less enticing period for tourists.

On Tristan da Cunha, spring is generally a mild period, marked by temperatures that range from highs of 20°C (68°F) to 17°C (62.6°F) and a corresponding dip in the lows from 16°C (60.8°F) to 13°C (55.4°F). Rainfall maintains a steady climb throughout spring, culminating in a monthly average of 155mm (6.1") in November. The daylight hours begin to increase, ending at 10.1 hours, while the sea temperature gradually cools off to 16°C (60.8°F).

Summer weather on the island reintroduces milder conditions with high temperatures moderating at around 15°C (59°F) while the lows settle at around 11°C (51.8°F). The rainfall achieves its peak, recording up to 160mm (6.3") during January and February, alongside 23 rainfall days. Correspondingly, the sunshine hours increase to an average of 3.4 hours per day, while the UV index is at its lowest, dropping to 2.

Autumn in Tristan da Cunha comes with a dip in temperatures, with lows descending to 10°C (50°F) and highs hovering around 14°C (57.2°F). Rainfall remains significant during these months, peaking at 175mm (6.89") in August with 26 rainy days. Daylight hours start to increase from 9.9 hours in July to 10.7 hours in August before extending further by September.

Winter ushers in the coolest period on Tristan da Cunha, with the lowest temperatures dropping to 10°C (50°F) and high temperatures settling at about 15°C (59°F). Despite this, the rainfall sees a decline, tapering off to monthly averages of 151mm (5.94") and 128mm (5.04") in October and November respectively. The sunshine hours start to improve, ending winter with average of 4.6 hours per day, while daylight hours increase significantly, ending at 14.1 hours in November.

Presenting as the initial month of the year, January's weather in Tristan da Cunha sets the tone for rest of the tropical year. The island experiences light rainfall interspersed with sunny intervals. While sunshine duration is relatively low, the UV index stands highest in the year at 12 units. Weather in January »

February ushers a similar weather pattern as January but with a rise in several parameters. At 113mm (4.45"), rainfall observes a noticeable increase while daylight duration and UV index fall to 13.5 hours and 10 units respectively. Weather in February »

March might witness a minor spike in temperature but the overall climatic pattern remains almost identical to February. Rainfall continues to climb, touching 121mm (4.76"), and there's a narrow drop in the duration of daylight hours. Weather in March »

April, the first month of autumn in Tristan da Cunha marks the diminishing intensity of sunlight with both daylight and sunshine hours recording a declining trend. With rainfall increasing further to 129mm (5.08"), showers become a frequent phenomena in April. Weather in April »

May introduces the onset of a chilly atmosphere as Tristan da Cunha steps into the comfort of cooler months. Sea temperatures continue to drop further, coinciding with the falling atmospheric temperatures. A rise in rainfall up to 155mm (6.1") is a poignant characteristic of this month's weather. Weather in May »

June is marked by a lower temperature range while rainfall encounters a steadily high level of 160mm (6.3"). The least amount of daylight i.e., 9.6 hours, paired with the least volume of sunshine are the noticeable characteristics of June’s weather. Weather in June »

July carries forward the cool vibe of June, albeit with raised precipitation upto 160mm (6.3") as the standout characteristic. The weather is evocative of typically cold months, emphasized by the addition of a slight drop in sea temperatures. Weather in July »

August stands unchallenged as the rainiest month in Tristan da Cunha with rainfall stretching up to 175mm (6.89"). Concurrently, the UV index bottom marks at two units in this month, standing in contrast to the high precipitation numbers. Weather in August »

Winter gently gives way to spring in September with sunlight hours slowly gaining some momentum while the temperature begins to climb. A significant characteristic of September's weather is the drop in rainfall to 169mm (6.65") which provides a slight respite after a pronounced wet spell. Weather in September »

October brings a noticeable decline in rainfall, which falls to 151mm (5.94"), as the weather starts to dry up. This coincides with a steady increase in temperatures, setting the stage for the approaching summer months. The sea temperature, daylight hours, and sunshine hours also increment slowly, signalling towards brighter and sunnier days. Weather in October »

As the year’s end nears, November introduces a further rise in temperature, coupled with a continuation in the falling trend of rainfall which now drops to 128mm (5.04"). The transformational shift of weather from rainy to relatively warmer and sunny unfolds during this period, making the outdoors alluring for activities and sightseeing. Weather in November »

December, the final chapter of the year in Tristan da Cunha, ushers in a temperate climate. A notable feature in this month is the abundant daylight hours at 14.7 that paints long and bright days. The sea temperature witnesses a rise, matching up to the hiking atmospheric temperatures. Weather in December »