Two national weather warnings have been issued.
A rainfall warning comes into place from 7pm Thursday August 8th.
Met Eireann are predicting that heavy rain will spread from the south Thursday evening and night.
Accumulations of 25 to 40mm will occur over a relatively short time period with spot flooding likely.
The weather warning covers all of the county and is in place until Friday morning at 7am.
A separate thunderstorm warning is in place from 6am Friday until 10pm Friday 9th.
Forecast for Connacht
Early Thursday night a spell of heavy rain over the south will spread further northwards with the risk of thundery downpours. Easterly winds will increase fresh to strong and gusty but moderate towards morning. Lowest temperature will stay around 13 to 15 degrees.
During Friday morning heavy rain will clear from the north. Elsewhere scattered showers will become heavy or prolonged with the risk of thundery downpours. Top temperatures of 20 to 22 degrees in light to moderate southerly breezes, but fresh near south and east coasts.