Heavy downpours have caused flooding and traffic disruption in parts of Northern Ireland as forecasters issued an amber thunderstorm warning.
The Met Office warned of high water affecting homes and businesses and said power cuts were likely as the heatwave broke with torrential rainfall.
Belfast International Airport recorded 74.4mm between midday and 3pm on Saturday.
The average Northern Ireland rainfall for the month of July is 81.2mm.
A Met Office statement said: “Slow-moving and at times torrential rain accompanied by thunder and lightning will affect parts of Northern Ireland through this afternoon.
“Where the heaviest rain occurs some surface water flooding is likely.”
Motorists were asked to avoid the underpass at Stockman’s Lane in Belfast due to high water levels.
Cars parked along the hard shoulder on the A1 near Dromore in Co Down and there were significant delays in both directions on the arterial route.
In an amber warning covering every county of Northern Ireland except Fermanagh, the Met Office said the rain and thunder will ease from the south later this afternoon.
Rainfall accumulations of up to 30mm in the hour and 60 mm in three hours are likely in places, though many areas will see lower rainfall amounts.
Traffic Watch Northern Ireland said: “Following heavy rainfall around midday we had reports of flooding on many roads in the Greater Belfast area – things have improved noticeably in the last half hour but road users are advised to slow down and drive appropriate to the conditions they are encountering.”
Flooding near Hilltown in Co Down also created long queues of traffic.
Transport operator Translink cancelled some buses.
The Met Office in Northern Ireland issued a severe weather warning, extended until 7pm on Saturday.
Police warned of flooding on the A1 southbound, between Gowdystown Road and Banbridge.
“Passable with care, please avoid the area if possible and exercise extreme caution.”
Officers advised drivers to slow down and take care.
In the Republic, status yellow rainfall warnings were issued.
Downpours were expected to affect the whole of Leinster, Cavan, Monaghan, Donegal and Waterford.
The Road Safety Authority urged drivers to watch out for flash flooding and the risk of aquaplaning.
The AA reported very wet road conditions in parts of Wicklow, Meath, Mayo and Cavan.
The rainfall brings to an end a heatwave which has left parts of the south and east badly affected by dwindling water supplies in the country’s reservoirs.
A hosepipe ban is still in place in the Republic.
Water engineering experts believe the situation will remain “critical” up to and possibly beyond mid-August, Irish Water said.
It added: “The board reviewed the latest available data on water usage and the condition of the raw water sources around the country and have confirmed the extension of the timeline of the water conservation orders, or hosepipe bans for the Greater Dublin area and nationally until the 31st of August and a continuance of the level two water pressure reductions in the Greater Dublin area for another two weeks.”