The extent of the flooding and related damage is far less than in 2012, when three million people's homes were flooded and 1.4 million people were displaced in Nigeria alone.
While rainfall has been average to above average across much of the region, there have been deficits in some areas, especially in and around the Gulf of Guinea, with Benin, Ghana, Liberia, western Nigeria and Togo most affected, according to the National Oceanic and Atmospheric Administration (NOAA). Food security experts fear harvest prospects will decline in affected areas.
Niger is the most seriously affected country in the region, with 75,000 people in need of humanitarian assistance, according to a government statement released in early September. In the capital, Niamey, some 3,000 gardeners and farmers who planted along the Niger River lost their harvests, according to the Federation of Nigerien Market Gardeners' Cooperatives (FCMN).
According to the government, 70 wells across the country have collapsed or been submerged, and 13,000 irrigation ditches and dykes have been destroyed, including some that were built following extensive flooding in 2012.
"We watched the river water rise quickly. Within hours all of our vegetables were flooded," said Salifo Lompo, a market gardener in Komo, a Niamey neighbourhood.
In the Bangabana neighbourhood on the bank of the river, a dyke that had been built to stop flooding in one set of fields instead caused flooding in the neighbouring fifth district, according to residents, causing members of the two communities to come to blows. The government eased tensions by pumping water from the area.
Thus far, the government has released US$124,000 to respond to the crisis and called for international and national support.
According to OCHA, 7,924 people have been displaced and 81,506 have been affected in Nigeria's Abia, Zamfara, Bauchi and Kogi states. According to NOAA, high water levels at the Kainji, Shiroro and Jebba dams in southern Kebbi and Niger states have elevated the risk of floods along the Niger River.
The Ministry of Health, the National Emergency Management Agency (NEMA) and State Emergency Management Agencies, the International Committee of the Red Cross and the UN Children's Fund (UNICEF) are responding to the needs of flood-affected people. NEMA will set up two camps for displaced people in Bauchi State.
"The magnitude of the floods requires a joint strategic action plan, as we must go far beyond emergency response measures given the reality of the anticipated flood of this year," Francis Doukpola, chairman of Bayelsa State's post-flood management committee in the Niger Delta, said on 2 September.
In 2012, Nigeria experienced its worst flooding in 40 years, with 1.44 million people displaced and 30 out of 37 states affected.
Some 10,000 people in Benin have been displaced by floods, among 33,000 affected, and 21,000 hectares of land are thought to have been damaged, according to OCHA. Critical needs include tents, food and health supplies. The National Civil Protection Agency and UN Resident Coordinator's office are coordinating flood response, says OCHA.
In Burkina, 602 homes have been destroyed by floods, and 6,712 people have had their homes, businesses or fields flooded.
According to the Gambian government, 216 people have been displaced by floods and two killed.
Guinea's capital, Conakry, was heavily flooded, affecting 11,106 nationwide.
Mali's capital, Bamako, has experienced consistent, heavy rains, causing severe flooding in some neighbourhoods, according to the government and the International Organization for Migration (IOM). Two rain storms hit the city, causing severe flooding, according to IOM. Some 37 deaths have been reported, 20,000 people have been displaced, and 280 homes have been destroyed. IOM, aid groups and government agencies are distributing assistance in communes 1 and 4, which were the worst affected.
In Mauritania, 2,305 people were displaced among the 4,225 whose homes, fields or businesses were flooded. Countrywide, close to 800 homes have been damaged or destroyed, according to OCHA.
In Mauritania - as well as in Niger, Mali and northeast Chad - there is risk of an increase in locust infestations as a result of heavy rains, according to the World Food Programme.
Between 73,500 and 105,000 homes have been flooded, mainly in and around the capital, Dakar, as well as in Fatick and Kaolack in central Senegal, and in Kedegou in the southeast, according to OCHA.
The government is pumping floodwater from towns across the country, and is spraying mosquito repellent to try to control disease outbreaks. UNICEF, World Vision, the Senegalese Red Cross and other partners are distributing assistance to the most vulnerable.
This article was produced by IRIN News while it was part of the United Nations Office for the Coordination of Humanitarian Affairs. Please send queries on copyright or liability to the UN. For more information: https://shop.un.org/rights-permissions