At one stage the N56 from Letterkenny was tailed back beyond Illistrin where flood defences of the new stretch of road failed once again to cope with the downpours.
Dozens of millimetres of rain fell between 6.30pm and 9pm and lightning lit up the dark skies.
Roads in Ramelton were badly flooded. Homeowners in Ballyare fought a running battle with the flood waters, but sandbags proved useless in dealing with the deluge.
In Glenswilly the downpour sent mud sliding down lane ways and into homes.