Northern Ireland has provisionally recorded its highest ever temperature for the third time in less than a week.
A weather station in the city of Armagh recorded a temperature of 31.4 C at 15.20 on Thursday.
An amber warning for heat has been issued by Met Office the until the end of Friday.
The previous record of 30.8C stood for 38 years.
The Met Office has still to officially verify this week's temperatures.
Northern Ireland has once again provisionally broken its highest #temperature on record ????— Met Office (@metoffice) July 22, 2021
Armagh reached 31.4 ??C at 1520 this afternoon???????
This beats the 31.2 ??C that Ballywatticock recorded on Saturday and the 31.3 ??C that Castlederg recorded yesterday #UKHeatwave #heatwave pic.twitter.com/lItf4fwt8Z
NI Water has also asked the public to "use water responsibly" as there is a "possibility" that a hosepipe ban may be introduced.
In response, Lisburn and Castlereagh City Council have turned off all water features in the area, including the water jets in Lisburn's Market Square.
The council said it had taken the precautions due to increased temperatures and "the need to protect our water supplies".
Ticket sales suspended
The hot weather caused disruption to travel in parts of Northern Ireland on Thursday.
Rail services were delayed after speed restrictions were put in place due to high track temperatures.
Ticket sales to Helen's Bay, County Down, were also suspended in an attempt to manage the large number of passengers travelling to the area.
Translink said it had taken the decision to manage capacity for return journeys.
It asked people to consider whether their journey was "completely necessary" and to allow extra time for travel.
Infrastructure Minister Nichola Mallon said people should avoid visiting places where there is a chance large numbers of people will gather.
Ms Mallon said the high temperatures have also affected the road network, with bitumen in some roads having softened.
Heat exhaustion and sunburn
The Met Office issued the extreme heat warning, with Met ??ireann warnings also in place in the Republic of Ireland.
The Met Office warning comes with an appeal to watch out for heat exhaustion and sunburn.
Elsewhere, the Republic of Ireland recorded its first tropical night for 20 years.
Temperatures on Valentia Island, County Kerry, one of Ireland's most westerly points, did not fall below 20.5C overnight on Wednesday.
Tropical nights, meaning shaded air remains above 20C all night, are rare in Ireland, having previously only been recorded six times.