The warning, issued on Monday, covers all six counties, Antrim, Armagh, Down, Fermanagh, Londonderry and Tyrone and will remain in effect throughout Tuesday.

Forecasters said between 20mm and 30mm of rainfall is expected over an 18-hour period, with higher ground such as the Mourne Mountains likely to receive more than 40mm.

Heavier bursts could see 10–20mm fall within just a few hours, raising the risk of surface water flooding and hazardous travel conditions.

A Met Office spokesperson said the rain “will arrive across Northern Ireland early on Tuesday morning, with some heavy bursts developing during the afternoon and evening before clearing later in the night”.

The public is being advised to prepare for longer journey times and possible disruption to public transport. Bus and train

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