More local authorities could put water restrictions as Met Éireann says Ireland will be in a state of "absolute drought" by this evening.
Some councils have already banned the use of hosepipes in a bid to conserve water - and others are warning they may soon follow.
The dry weather is set to continue well into next week - with Met Éireann forecasting temperatures in the high twenties.
"An absolute drought is defined as a period of 15 days with less than 0.2mm of rainfall," said Gerry Murphy from Met Éireann.
"For some parts of the eastern country, this status has been reached - yesterday, actually, in the Dublin region - and that would extend to other parts of the country then today."
Met Éireann are also advising that the hot weather will continue into next week, and that the sunburn index remains high.