"People are experiencing vomiting and diarrhoea. These are the first indicators that diseases such as cholera, dysentery and typhoid are taking root," said Anthony Mwangi, the KRCS public relations manager.
The KRCS identified Mpeketoni area of Lamu district and Witu in neighbouring Tana River as the worst-affected, saying heavy downpours during the first week of June inundated villages in the two areas, damaging crops, homes and killing livestock.
A total of 10,218 people have been affected by the floods in Mpeketoni and Witu. The Mukuru bridge in Mpeketoni was washed away, leaving dozens of children unable to get to school.
The unusually heavy long rains should have subsided by the end of May in the Coastal Province, but have continued in many parts of the region with devastating effects. In Kilifi district alone, 5,700 people are affected by flooding, which also hit Mombasa, Malindi and the Kipini area of Tana River district.
There are fears that malaria could spread fast, with stagnant water providing ideal breeding conditions for mosquitoes. The KRCS has been distributing mosquito nets in a bid to prevent malaria epidemics.
Flooding also destroyed pit latrines and sewage infrastructure, exposing drinking water sources to easy contamination.
The affected people need medical care, clean water, food, bed nets, kitchen sets, soap and water purification tablets. Farmers also require seeds to replant where crops were destroyed.
In its June-August weather outlook review released on 30 May, the Kenya Meteorological Department called for contingency plans to assist communities likely to be affected by flooding along the coastal areas and rainfall failure in other parts of Kenya.