Ghana’s climate is tropical, driven by its location in West Africa, just north of the Equator on the Gulf of Guinea. This ensures consistently warm to hot temperatures throughout the year. Specific weather conditions vary significantly across the country, influenced by the interplay between moist Atlantic air masses and dry air from the Sahara Desert.
The Three Major Climatic Regions
Ghana’s climate is divided into three major zones, each with distinct temperature, rainfall, and humidity profiles. These regional variations are determined primarily by latitude and proximity to the coastline.
The Coastal Savannah region, including cities like Accra, receives the lowest annual rainfall, ranging from 700 to 850 millimeters. Temperatures average around 26°C, but humidity remains elevated due to the nearby ocean. Rainfall on the eastern coast is lower than a short distance inland, a phenomenon attributed to the coastline’s orientation and the presence of a cool ocean current during heavy rain periods.
The Forest and Middle Zone, which includes areas like Kumasi, is the wettest part of the country, with annual rainfall exceeding 1,500 millimeters. The high moisture content results from warm, humid air masses from the southwest monsoon. This zone experiences high humidity, often between 75% and 80%, and mean temperatures around 27°C, peaking near 31°C in the hottest months.
The Northern Savannah region, encompassing the upper reaches of the country, is characterized by the most extreme temperature fluctuations and the lowest overall humidity. Annual rainfall totals 1,000 to 1,100 millimeters. Temperatures can soar to over 35°C during the day in the dry season but drop sharply at night, creating a wider daily temperature range than the southern regions.
Understanding Ghana’s Seasonal Cycles
Ghana’s climate is defined by distinct seasonal cycles of wet and dry periods that vary significantly between the north and south. The timing and intensity of rainfall are governed by the movement of the Inter-Tropical Convergence Zone (ITCZ), the boundary where moist, equatorial air meets dry, continental air.
Southern Ghana, including the Coastal and Forest zones, experiences a double maxima rainfall pattern with two distinct rainy seasons each year. The major rainy season runs from March or April to July, followed by a short break, and then a minor rainy season occurs from September to November. This pattern is crucial for agriculture, as the major season often brings the heaviest precipitation.
Northern Ghana follows a single maxima rainfall pattern with one long rainy season lasting from May to September, peaking in August or September. This is followed by a long dry season that lasts from October or November through April. Temperatures across the country are highest just before the rains begin, typically in February and March, and slightly cooler during the major rainy seasons due to increased cloud cover.
The Impact of the Harmattan Wind
The Harmattan wind is a dry, continental trade wind that originates from the Sahara Desert and blows across West Africa from the northeast. It occurs during the dry season, starting in late November or December and lasting until February or March. Its primary effect is a significant reduction in atmospheric humidity, sometimes plummeting below 15%.
The Harmattan causes days to be hotter, sometimes exceeding 35°C, while nights become cooler, especially in the north. The wind carries fine dust particles, creating haze that reduces visibility and affects air quality. This haze impacts air travel and poses health risks, particularly by exacerbating respiratory conditions. The intense dryness increases the risk of bushfires and can lead to water stress for crops and natural vegetation.