The Republic of Sudan, located in Northeast Africa, is a massive country whose size and latitudinal span create complex climate conditions. Extending from the hyper-arid Sahara in the north toward the tropical zones of the south, the nation experiences a profound north-to-south gradient in weather patterns. Local climates are highly diverse, determined primarily by the amount and reliability of annual rainfall. Understanding Sudan’s climate requires looking at distinct zones, each with characteristic temperatures and precipitation cycles.
Major Climatic Regions of Sudan
The climate of Sudan is broadly classified into three major zones, shifting dramatically as one moves away from the Mediterranean influence toward the equator. These classifications are based on temperature and precipitation patterns. The spectrum ranges from the driest conditions in the extreme north to the wettest conditions in the far south.
The extreme northern part of the country, bordering Egypt, falls under the Arid Desert Climate (BWh). This zone is characterized by virtually no rainfall, with some areas experiencing years without measurable precipitation. Summer temperatures are extreme, routinely exceeding 43°C, and occasionally reaching 50°C. A significant feature is the high diurnal temperature variation, where daytime heat falls rapidly after sunset, leading to much cooler nights.
Moving southward, the climate transitions into the Central Belt, defined as the Semi-Arid Steppe Climate (BSh). This region receives a small, highly unreliable amount of annual rainfall, typically ranging from 75 mm to 300 mm. This minimal moisture is usually concentrated in one or two brief months following the hottest period. The semi-arid climate acts as a transitional zone between the desert and more humid regions, supporting short grasses and scrubby vegetation.
The southern regions experience a Tropical Wet and Dry or Savannah Climate (Aw). This climate is defined by consistently high temperatures year-round and distinct alternating wet and dry seasons. Annual rainfall totals are significantly higher and more dependable, ranging from 700 mm to 1,200 mm. The rainy season is much longer than in the north, lasting for up to seven months in the far south.
Geographic and Atmospheric Influences
The climatic diversity across Sudan results directly from large-scale atmospheric systems and physical geography. The most prominent factor is the seasonal migration of the Intertropical Convergence Zone (ITCZ). The ITCZ is a low-pressure belt near the equator where trade winds meet, causing air to rise and leading to heavy precipitation and thunderstorms.
The ITCZ moves northward during the Northern Hemisphere summer, bringing the rainy season to Sudan. As it pushes north, it draws moisture-laden southwesterly winds from the Congo Basin over the country. This movement determines the length and intensity of the wet season. The far south experiences the ITCZ for the longest period, while its northern limit is around Abu Hamad.
Conversely, the proximity of the Sahara Desert exerts a continuous drying influence, especially in the north. During the Northern Hemisphere winter, the ITCZ retreats southward. The country then falls under the influence of dry, hot air masses originating from the desert. This creates a conflict between two major wind systems: the dry, hot northerly winds, often referred to locally as the Harmattan, and the moist, rain-bearing southwesterly winds.
The dry northerly winds dominate for most of the year in the northern two-thirds of Sudan, limiting cloud formation and precipitation. The strength of the southwesterlies determines how far north the annual rains will penetrate. This dynamic balance between the dry continental air from the north and the moist tropical air from the south dictates the climate experienced in any given region.
Annual Seasonal Weather Patterns
The year in Sudan is typically divided into three observable seasons based on temperature and precipitation, though timing varies significantly from north to south. The Hot Dry Season generally occurs from March to May, before the onset of summer rains. During this period, temperatures reach their annual peak, often soaring above 40°C across the central and northern regions.
The air is extremely dry, and cloudless skies allow for maximum solar radiation, contributing to the intense heat. This season is particularly harsh in Khartoum, with average high temperatures reaching 41°C in May and June. The extreme heat often precedes the arrival of the moist air flow.
The Rainy Season typically lasts from June to September, though it can begin as early as April in the far south. Rainfall is characterized by short, intense storms rather than prolonged drizzle. The total yearly amount is often delivered in just a few heavy events. The arrival of the moist southwesterly air causes a notable rise in humidity, which can make the heat feel stifling, particularly in the central and southern regions.
The Cooler Dry Season begins around October and lasts through February, as the dry northerly winds reassert their dominance. Temperatures during this time are the most comfortable of the year, with daytime highs around 32°C and night lows dropping to 15°C in central areas. This season is also marked by the frequent occurrence of Haboobs, which are violent dust storms. These storms form when the downdraft of air from an approaching thunderstorm lifts massive walls of sand and clay, temporarily reducing visibility to zero.