Thailand has been warned to brace for three storms, with the first set to make landfall today, according to the Thai Meteorological Department (TMD).
The department on Saturday issued a strong warning that Tropical Storm Lionrock will sweep into upper Vietnam where it will downgrade to a tropical depression.
The upper part of the Northeast is expected to take a battering.
Lionrock is expected to unleash heavy rainfalls until Tuesday, said Team Consulting Engineering and Management Plc, or "Team Group", which analyses storm situations.
The team said there has been confirmation of two other storms which are brewing and likely to influence the weather in Thailand after Lionrock.
The confirmation was made by Tropical Storm Risk website and weather analysis agencies in the UK and Japan, said Team Consulting CEO Chavalit Chanthararat.
One of the two further incoming storms, Kompasu, is being closely watched as there is still uncertainty over how hard it will hit the Vietnamese city of Danang and capital Hanoi and whether it will dissipate by Thursday.
Parts of the Thai Northeast and Central Plains, as well as the eastern and western provinces, should prepare for heavy rain in the latter half of the week, warned Mr Chavalit.
After that, a tropical depression now brewing in the South China Sea could trigger more wet weather for Thailand from next weekend onwards, said the Team Group CEO. If the three storms were all to hit hard or coincide, flooding could result in many areas lasting until early next month, he said.
In response to the approaching Lionrock storm, Interior Minister Anupong Paojinda has ordered governors of all provinces to prepare for further floods in the coming days and where necessary, follow emergency response procedure.
Yesterday, the National Water Command's Facebook page reported that levels in the country's main rivers, except those in the North, were likely to rise. At the moment, each reservoir is about 69% full on average.
Sixteen reservoirs in danger of overflowing include Kwae Noi Bamroong Daen, Thap Salao, Lam Phra Ploeng, Lam Takong and Khun Dan Prakan Chon.
Witsanu Attavanich, a Kasetsart University expert in climate change, said yesterday the last lap of the rainy season could bring above-average rainfall.