Households could face a loss of water supply if the current hosepipe ban is not adhered to, NI Water has said.
As well as issuing further advice on water conservation, the water company said the ongoing heatwave meant customers were using water “faster than we can treat it and get it into supply,” and that some supplies in rural areas of Tyrone and Armagh had already been interrupted.
The public have also been reminded that the hosepipe ban – for domestic users only – remains in place.
A spokeswoman for NI Water said: “Please only use what you need to. We may be surrounded by water, but did you know that despite our planet being covered in water, only 1% of it is actually drinkable?
“We would hope that people will voluntarily work with us to reduce their water usage over the coming days. A loss of water supply for households is a completely avoidable situation; however, if people continue to use water at the current rate, the loss of supply could become a reality.”
The spokeswoman added: “Unnecessary use of water ie washing cars, watering lawns etc, is putting the water supply of your own household and that of your neighbours at risk. If everyone simply uses the water they actually need, there will be plenty for everyone.”
The hosepipe ban became effective in Northern Ireland at 6pm on Friday as temperatures reached 30C for a third successive day.
NI Water has warned that a fine of up to £1,000 can be imposed if the ban has to be enforced.
Met Office forecaster Robin Steel said: “The top temperature on Saturday was at Magilligan which was 27.3C, followed closely by Castlederg which was 27.1C.
“The Giant’s Causeway was 26.7C. The average daytime maximum for early July is around 18C typically.”
There was a sharp contrast yesterday between the warmest and coolest areas of the Province, with lows of 13C on a largely cloudy north coast compared to 23.6C in south Down and Co Armagh.
“I think we will get rid of that low cloud around the north coast for Monday and the temperatures will be very similar to today (Sunday), probably around the 25C mark.
“The top temperatures again will be in Co Down and Co Armagh, and maybe in Fermanagh.”
The forecaster added: “Most, if not all, of the week ahead will continue with a lot of sunshine and very warm temperatures ... although I wouldn’t rule out the outside chance of a shower from midweek on. But most places will stay dry and sunny.”
John Wylie of the Met Office described the current heatwave as an “extraordinary spell of high temperatures,” and added: “It is rare, even in high summer, to get three days of 30+C. July 2013 was the second hottest calendar month on record, but only one day was over 30C.”
The hot weather has put farmers on high alert for the outbreak of wildfires, with the Ulster Farmers’ Union warning that “any ignition, like a cigarette butt or disposable barbecue, could result in an unpredictable fire”.
In some areas gritters – a sight more usually associated with winter – have been deployed, spreading crushed rock dust on to melting roads to create a non-stick layer between the surface and vehicles.
The Met Office issued a weather warning for thunderstorms on Sunday – the first such advisory since the service was introduced. Forecasters said storms could bring torrential rain, hail and lightning to places in south-west England and Wales.
The yellow warning was in place between 6am to 10pm due to high levels of humidity.