Met Éireann has upgraded its severe weather warning tonight to status orange for County Donegal.
After a fine day of summer sun and fine temperatures, they are now anticipating spells of very heavy and thundery rain, starting from midnight tonight.
The upgraded weather alert is active for counties Donegal, Leitrim and Sligo, and will last until 4am on Monday morning.
The national weather forecaster is warning of localised flooding and very difficult travelling conditions on the roads.
The prior status yellow warning that applies to much of the country will also still come into effect from 10pm tonight, and last until 7am tomorrow morning.