The climate on Ascension may be sub-tropical, but it is much cooler and drier than that would suggest, with temperatures kept relatively moderate by the persistent southeast trade winds.
At sea level, they average around 79°F (26°C) year-round, peaking in the mid 80s (30s) during the early part of the year, when humidity can be quite high. On Green Mountain, it’s usually about 10–15°F (4–7°C) cooler.
Showers occur throughout the year, with a tendency to being heavier around February and March, but Green Mountain is considerably wetter than the lower-lying areas.
Although St Helena is located in the tropics, her climate is kept generally mild by the southeast trade winds. Despite the vagaries of global warming, summers are generally hot and sunny, and winters cool and mild (though locals would say cold and wet!).
That said, there are noticeable climatic differences between Jamestown, located on the northern coast, and the interior of the island. Jamestown can be sunny and humid, while at the same time Longwood could be experiencing cool mists and a higher amount of rainfall.
Rainfall, while possible at all times, tends to peak in March/April and August, though this, too, varies considerably with elevation. Jamestown averages around 4in (100mm) of rain a year, a figure that rises to 43in (1,083mm) at Scotland, in the district of St Paul’s, at around 2,130ft (650m) above sea level. Similarly, temperatures vary at different points around the island.
In Jamestown, the warmest area on the island, the maximum daytime temperature ranges from 19–37°C (66 to 99°F), while the interior – which is at a higher elevation – is considerably cooler, with the maximum daytime temperature ranging from 18– 24°C (64 to 75°F ). Humidity varies between 70% and 85%.
The main tourist season on St Helena is from November to March, when it is summer in the southern hemisphere and the days are predominantly sunny and hot.
You can expect some rainfall, especially out of Jamestown in March, but rarely does it last long at this time of year. Between April and October there are fewer tourists, but it is noticeably cooler than in the summer months, and generally wetter too.
St Helena is good at festivals. Colourful street parades draw big crowds, whether at Christmas or for one-off carnival occasions. If you’re on the island, keep an eye on the local paper for forthcoming events: perhaps a pancake race on Shrove Tuesday, or simply the Guides and Scouts marching to church on Mothering Sunday.
Its main festival is in November: the Festival of Running. This weeklong occasion, organised by the National Amateur Sports Association (NASAS) and the tourist office, claims to be the most remote running festival in the world. Held annually to raise funds for training local athletes, it incorporates seven events: a 3km fun run/walk, a 10km road race, a 15km trail run, a half and full marathon, a new triathlon, and of course an ascent of the 699-step Jacob’s Ladder.