A number of people were forced to leave their homes on Tuesday night because of flooding while several bridges across the north west collapsed because of the force of the floodwater.
People were also trapped in their cars while the Fire Service said they responded to 60 incidents overnight.
A Northern Ireland Fire & Rescue Service (NIFRS) Spokesperson said: “Northern Ireland Fire and Rescue Service are continuing to deal with a large number of flood related incidents across the province as a result of localised heavy rainfall.
“A considerable number of these incidents have occurred in the west of the province.
“Between 19:00 hours and 23:00 hours, NIFRS Regional Control Centre (RCC) has received a significant number of emergency calls. During this period, NIFRS has responded to 60 operational incidents in the West of the province, the majority of these incidents have been flood related.
“NIFRS has carried out a number of rescues of persons trapped in vehicles in flood water and we would advise all road users to exercise extreme caution overnight.”
A multi-agency response including the PSNI, NI Fire and Rescue Service, DfI Rivers and Roads, Northern Ireland Water and Derry City & Strabane Council is underway to deal with the impact of yesterday’s exceptional rainfall across the North West.
“Throughout yesterday evening and last night the agencies deployed all available resources to respond to a very high volume of calls from the public needing assistance & distribute sandbags .
Unfortunately the scale of the rainfall & associated flooding resulted in the significant flooding to homes and businesses in the area. Many key roads across the North West were closed for a period which hampered the agencies responding to calls.
“Rainfall amounts of 60mm or more were recorded over the last 24 hour period which when compared to the Northern Ireland average rainfall amounts for all of August of less than 100mm, highlights the challenge that the multi-agency response faced.
“The response of all the relevant agencies is ongoing as we continue to work together to try to reduce the impact of this severe disruption.
“Efforts are currently focused on ensuring those at most risk are provided with assistance.
A number of roads across the North West area became impassable because of flooding.
They included the Glenshane Pass, the Victoria Road from Londonderry to Strabane at Prehen and the village of Magheramason just over the border in County Tryone.
Floods closed roads in the Co Londonderry villages of Eglinton and Greysteel.
Bridges collapsed in Claudy and Drumahoe, while Institute’s Riverside stadium in Drumahoe was left underwater when the River Faughan burst its banks.
Water also seeped into City of Derry airport damaging buildings including the departure lounge.
There were also road closures in Donegal at the Cross Border Road.
Police issued a warning to motorists of the dangers of dislodged manhole covers on roads hidden by floodwater.