Senegal sits between latitudes 12° and 17° north, straddling the Sahel transition zone where West African coastal climate systems meet desert air from the interior. The country experiences two distinct seasons governed by the West African monsoon: a dry season from November through May and a rainy season from June through October. This binary pattern determines nearly every aspect of travel logistics, from road conditions in Casamance to bird populations at Djoudj National Bird Sanctuary to ocean temperatures off the Dakar Peninsula. The timing question is not about finding moderate weather—Senegal offers little of that—but about aligning your tolerance for heat, humidity, and precipitation with specific activity windows that open and close according to predictable meteorological cycles.
The dry season from November through February represents peak travel conditions by most metrics. Dakar records average daytime temperatures between 24°C and 28°C during these months, with nighttime lows around 18°C to 20°C. Humidity drops to 40-50 percent, and rainfall is functionally zero—Dakar receives less than 5 millimeters total between November and April. The harmattan wind arrives intermittently from December through February, carrying fine Saharan dust that reduces visibility and creates hazy skies but also suppresses humidity. This northeastern trade wind can drop nighttime temperatures in interior cities like Tambacounda to 15°C, requiring layered clothing despite daytime heat reaching 32°C to 35°C. Saint-Louis and the Senegal River valley experience the harmattan most intensely, with dust sometimes thick enough to ground small aircraft at the regional airport. The bird sanctuary at Djoudj reaches peak migratory populations in December and January, when Palearctic species including garganey ducks, ferruginous ducks, and purple herons concentrate along permanent water in numbers exceeding one million individuals according to Wetlands International surveys. Beach conditions along the Petite Côte from Saly to Mbour are optimal—water temperatures hold at 22°C to 24°C, Atlantic swells moderate to 1-2 meters, and northwesterly winds average 15-20 kilometers per hour.
March through May constitutes the hot dry season, when Senegal reaches annual temperature peaks. Dakar sees daytime highs climb to 30°C to 32°C, but interior regions cross into physiologically challenging territory. Tambacounda regularly exceeds 40°C in April and May, with 2019 recording a national high of 48.8°C at Matam on the Senegal River. The Ferlo Desert and surrounding semi-arid zones experience surface temperatures above 50°C during midday hours. Humidity remains low at 30-40 percent until May, when pre-monsoon moisture begins infiltrating from the south. Dust concentration in the air decreases as harmattan winds subside, improving visibility but increasing solar radiation intensity. This period sees the lowest tourist numbers—Gorée Island ferry operators report 40 percent fewer passengers in April compared to January, and hotels in Dakar routinely offer 30-50 percent discounts on published rates. Wildlife viewing in Niokolo-Koba National Park reaches annual peaks because vegetation dies back and animals concentrate around the Gambia River and permanent waterholes, but access depends on heat tolerance. Park authorities recommend game drives before 10:00 and after 16:00 only. The Great Mosque of Touba hosts the Grand Magal pilgrimage in the Islamic month of Safar, which shifts annually on the Gregorian calendar—the 2024 observance occurred in early September, but it will move progressively earlier, landing in March-April timeframe around 2030-2031. When Magal falls during hot season, Touba's population swells from 1 million to an estimated 4-5 million pilgrims within 48 hours, straining water and transport infrastructure.
The rainy season begins erratically in June, consolidates in July, peaks in August and September, then cuts off sharply in October. Total annual rainfall increases from north to south: Saint-Louis receives approximately 200-250 millimeters, Dakar 500-600 millimeters, and Ziguinchor in Casamance 1200-1500 millimeters. The rain arrives in intense afternoon or evening convective storms lasting 1-3 hours rather than all-day drizzle. Dakar typically experiences 8-12 rain events per month during July through September, with individual storms dropping 40-80 millimeters. Humidity climbs to 70-85 percent, and temperatures moderate slightly—Dakar averages 27°C to 30°C, which feels more oppressive than dry season heat due to reduced evaporative cooling. The southern regions including Casamance, Kolda, and Tambacounda receive substantially more rain over longer periods. Ziguinchor records measurable precipitation on 15-20 days per month from July through September, with August totals sometimes exceeding 400 millimeters. Roads in Casamance transition from paved highways to laterite tracks that become impassable mud channels during heavy rain. The RN6 from Ziguinchor to Kolda is intermittently closed after major storms, and bush taxi drivers routinely refuse routes requiring river crossings at unimproved fords. Many lodges in Basse Casamance National Park close entirely from mid-July through September.
Agricultural transformation during rainy season is dramatic and economically determinative. The Sine-Saloum Delta, Niayes region, and Senegal River valley shift from dormant brown to active green within two weeks of first substantial rains. Millet and sorghum planting occurs in June, with fields reaching full height by August. Peanut cultivation—Senegal produces 1.5 to 1.8 million metric tons annually, making it Africa's third-largest producer after Nigeria and Sudan—follows the same cycle. Rice paddies in the Casamance River floodplain and along the Senegal River near Richard Toll are flooded and transplanted in July. This seasonal cycle creates visual landscapes vastly different from dry season photography, but also means rural populations are focused on fieldwork rather than tourism services. Cultural performances and traditional wrestling matches that occur weekly in dry season essentially cease during peak agricultural months.
Ocean conditions shift substantially with the monsoon. Water temperatures off Dakar rise from 24°C in May to 27°C to 28°C in September and October. Visibility for diving and snorkeling at Îles de la Madeleine National Park decreases from 15-20 meters in dry season to 5-10 meters during rains due to riverine sediment discharge and plankton blooms. Surf breaks along the Dakar Peninsula and at Toubab Dialao receive southern hemisphere swells from June through September, with wave faces reaching 2-3 meters compared to 1-1.5 meters during northern hemisphere swell season from November through February. Wind patterns reverse—the dry season northwesterlies give way to southwesterly monsoon flow averaging 10-15 kilometers per hour with higher humidity. Sport fishing dynamics change completely: blue marlin season off Dakar and the Petite Côte runs from April through June as fish follow temperature gradients northward, while sailfish arrive from November through February. Tarpon enter Casamance River estuaries during rainy season, with fish exceeding 50 kilograms caught near Ziguinchor from August through October.
Bird populations undergo complete turnover between seasons. The winter Palearctic migrants that dominate Djoudj National Bird Sanctuary from November through February depart by late March. Resident and intra-African migrants then predominate, including Abdim's stork, black crowned crane, and various herons, egrets, and ibises that breed during the rains when wetland productivity peaks. The Langue de Barbarie National Park at the Senegal River mouth hosts breeding colonies of royal terns, sandwich terns, and slender-billed gulls from May through August. Migratory shorebirds including bar-tailed godwits, whimbrels, and curlew sandpipers use coastal mudflats as stopover sites during northward spring migration in March through May and southward autumn migration in August through October. Birding during rainy season requires acceptance of difficult access and humid conditions, but breeding plumage and vocal activity compensate for reduced species diversity.