Map from Google - Ghana

In Ghana the climate is tropical, with a dry season in winter, and a rainy season in summer, related to the African monsoon. The rainy season lasts from May to September in the north, from April to October in the center, and from April to November in the south. On the contrary, along the east coast the rainy season is shorter and goes from April to June, with a break in July and August and a slight recovery in September and October.

Climates in Ghana

The rainiest area is the south, where precipitation is above 60 inches per year, and even more so the small portion of the west coast, where it reaches 80 inches per year. The driest areas are the north, where the rainfall amount is around 40 inches per year, and the eastern seaboard, including the capital Accra, where it drops below 30 in. Anyway, as we have said, in the north there's only one rainy season, reaching its height in the summer months, while in the coast the rainy season is divided into two.

Northern Ghana

In the center and north, winter is hot: daytime temperatures are usually about 95 °F in December and January, even though the air is dry and the nights are cool. Sometimes at night, however, the weather can get a little cold in the center-north, with lows around 50 °F.
From the desert, a hot, dust laden wind blows, called Harmattan. From February to April, the temperature increases further, easily surpassing 105 °F.
Here are the average temperatures of Bolgatanga, in the far north.
Average temperatures - Bolgatanga
Min (°F)667277797773727272726866
Max (°F)95991021009791888688939795

Then comes the monsoon. In March in the center and in April in the north, early showers and thunderstorms may occur, usually in the afternoon or evening, which become more substantial, exceeding 4 inches per month in the following month (ie April in the center and May in the north). Under the blows of thunderstorms and clouds brought by the ocean currents, the temperatures gradually decrease, and from July to September, during the period of the maximum rainfall, it drops to around 86/87 °F, but the humidity increases and the cloudiness is by now common.
The rains cease in October in the north, and in November the center; the return of the dry winds from the north produces a new increase of temperature: so both the sun and the heat come back. At the end of the year, rainfall amounts to 40 inches in the north and 47/51 inches in the center, where as we have seen the rainy season is longer.
Here is the average precipitation in Tamalé, in the north-central.
Average precipitation - Tamalé
Prec. (in)0.10.423.

In the south, the winter is a bit less hot, so that the daytime temperatures are about 88/90 °F in December and January, and arrive to 93 °F in February; here there is almost no warming in spring, because the rains begin as early as March.
Here are the average temperatures of Kumasi, located in the south.
Average temperatures - Kumasi
Min (°F)687272727272707070727270
Max (°F)909391908886828284868888

The rainiest month is June, with 9 inches of rain; from mid-July to mid-September the rains decrease a bit, and then they resume to fall from mid-September to early November. In the south, 55/60 in of rain fall in a year, even though east of Lake Volta and south-west of Kumasi the rainfall amount is even higher.
Here is the average precipitation in Kumasi.
Average precipitation - Kumasi
Prec. (in)

Lake Volta

Along the east coast, where the capital Accra is located, the climate is a bit different: winter is similar to that of the rest of the south, that is, less hot but more humid than the north, so that daytime temperatures are about 90 °F, and it remains around 73/75 °F at night. Sometimes, however, the dry Harmattan can arrive even here. Here are the average temperatures of Accra.
Average temperatures - Accra
Min (°F)737575757573737272757573
Max (°F)909191908884848284889090

In spring, rains arrive earlier, with early showers already in March, and a peak in June, when precipitation reaches 8 inches per month. But after the rains fall sharply, so much so that in August just 0.4 in of rain fall, because the so-called "Intertropical Convergence Zone", moves to the north. Nevertheless, from June to September, the sky usually remains cloudy. Even in the coast, as in the rest of the country, the summer months are the least hot of the year, and even here the humidity is high, indeed it is even higher than in inland areas, due to the proximity of the sea, but on the other hand there is the beneficial blow of the breeze, which reduces the feeling of stuffiness. In September and October, the rains resume a bit, but they do not reach 4 inches per month. In Accra, just 31 in of rain per year fall, and basically the only very rainy months are May and June, and sometimes the first half of July.
Here is the average precipitation in Accra.
Average precipitation - Accra
Prec. (in)0.61.433.15.77.720.

Along the west coast, the rains are much more plentiful, and from May to mid-July they become really heavy, reaching even 20 inches per month; the summer break is evident here as well, and runs from mid-July to mid-September, but then the rains return substantial, although they do not reach the peaks of the first part of the rainy season; the rains linger on until December, so that here the only relatively dry months are January and February, as well as August. In this area, the rainfall reaches 80 inches per year.
Here is the average precipitation in Axim.
Average precipitation - Axim
Prec. (in)

The sea in Ghana is warm enough for swimming all year round, although it gets a bit cooler from July to September.
Sea temperature - Accra
Sea (°F)818282848481777577818282

When to go

Generally, the best time to visit Ghana is winter, from December to February, because it is the driest and sunniest: the weather is generally good, although it's hot during the day in the center-north. In the north, the best time is from November to January, because February get even hotter. In November, in the south the last rains occur, and even in December on the west coast. So the best month to visit Ghana as a whole is January.

What to pack

In winter: in Accra and the coast, light clothes for the day, a light sweatshirt for the evening, scarf for the wind-borne sand and dust. In the north, light clothing, a sweatshirt and a light jacket for the evening, scarf for the desert wind.

In summer: tropics-friendly, light clothing of natural fiber, umbrella, a light sweatshirt and a light raincoat for the rain showers.