Ghana is a tropical country and it is hot year-round. The main factor in choosing when to visit is the rain.
The dry season (November to March) is the most popular time to travel. Humidity drops, skies are clearer, and roads are in better condition. December and January bring the Harmattan, a dry wind from the Sahara that carries dust and haze -- it makes the air feel cooler but visibility can be poor, especially in the north. Temperatures inland regularly hit 35°C and higher.
The wet season (April to October) brings heavy but usually short afternoon downpours. The south gets the most rain, with a peak around June. The north has a single rainy season from May to September. Travel is still perfectly possible during the rains -- roads can be muddy on dirt tracks, but main routes stay open. The landscape is lush and green, and tourist sites are less crowded.
For wildlife, the dry season is best. Animals in Mole National Park gather around waterholes between December and March, making them much easier to spot. The park is accessible year-round but walking safaris in the wet season can be challenging.
For beaches, the dry season is more comfortable, though the coast stays warm and swimmable all year. Sea conditions can be rough during the rainy months.
For festivals, the calendar is packed. The Homowo festival in Accra happens in August and September. The Chale Wote street art festival in Jamestown, Accra, takes place in August. Aboakyere, the deer-hunting festival in Winneba, falls in May. The Damba festival in Tamale and the northern regions is celebrated in July and August.
Budget travelers will find better deals during the wet season, when flights and accommodation are cheaper and there is less competition for services.