Update 2.10pm: Irish Water has thanked the public for reducing consumption, but says demand is still critically high.
The utility says water use in the Greater Dublin Area has fallen slightly.
Parts of the country have already seen outages in water supply including Athlone, Kilkenny, Longford and north Dublin.
The situation is being closely monitored in Donegal, Galway, Limerick and Mullingar.
As temperatures continue to soar, people are being reminded to take extra care in the sun with temperatures set to reach 30 degrees in some parts.
It will be cooler along coasts but the Irish Cancer Society says it is still important to apply good SPF and reapply regularly.
Earlier: Temperatures to hit 30 degrees; Irish Water warn supplies could be restricted
Temperatures are forecast to hit 30 degrees in many parts of the country today, as the heatwave continues.
Irish Water is warning that supply may have to be restricted in the Greater Dublin area if demand remains high.
Irish Water's Drought Management Team is meeting this morning to assess water supplies countrywide.
It says water restrictions will become unavoidable, because demand is very close to outstripping the supply available.
The utility's again urging households and businesses to limit water use.
Met Eireann's Joan Blackburn says today will be hot and sunny in many parts: "Particularly in western parts of the country over parts of Connacht and west Munster, we will see temperatures of about 30 degrees.
"Generally sunny conditions in most places though a bit of high cloud in southern counties at times making it a bit more hazy but really warm everywhere."