Met Éireann has issued a status orange national weather warning.
Widespread thundery activity is expected today, with the warning in place from midday until midnight.
Meanwhile, a less severe status yellow rainfall warning is in place for Connacht, Cavan, Monaghan and Donegal.
Some very heavy or thundery downpours are likely at times, mainly in parts of Connacht and Ulster, with local spot flooding.
That warning is in place from 11am until 9pm.