The Met Office has issued a yellow status severe weather warning for Derry and the rest of the North.
The warning will be active between 3pm and 11.55pm on Thursday October 19.
"Rain will spread into Northern Ireland on Thursday morning, turning persistent and occasionally heavy in the afternoon and lasting well into the evening before dying out. 20 to 40 mm of rain within 12 hours, (perhaps nearer 60 mm over the Mournes) falling on already very wet ground, seems likely to lead to flooding of some prone locations," the Chief Forecaster at the Met Office.
The weather warning comes hot on the heels of ex-hurricane Ophelia which swept through Ireland on Monday.
Three people in the south of Ireland were killed as a direct result of the storm.