Dublin householders and business owners must keep their hosepipes in their sheds from today after a ban kicked in at midnight.
However, while the capital normally runs into trouble with water supplies first, the problem is countrywide, with water levels in nearly nine out of 10 rivers below normal.
An assessment of the country's main water sources found 86pc of rivers, 75pc of lakes and 60pc of groundwater sites have levels below normal for this time of year.
In the case of rivers, 33pc are classified as running "particularly low", as are 40pc of lakes.
That was down to the parched conditions last month, and the situation has worsened since with the recent spell of hot, dry weather.
Twenty-seven water supplies around the country, including three in Dublin, are in drought, while 50 others are at risk.
Those supplies serve hundreds of thousands of people in 21 counties.
Only Cavan, Monaghan, Meath, Leitrim and Longford have so far escaped the drought warning.
Lack of rain is the underlying issue.
Last month was the driest May across the country since 1850, while the Greater Dublin Area had its driest spring on record.
The problem is made worse by the growing demand for water, with extra handwashing and cleaning becoming the norm in the effort to stave off coronavirus.
Added to that is the effect of the good weather in bringing gardening enthusiasts out to tend to thirsty plants, cooped up children enjoying paddling pools and cars getting their first wash in weeks.
Irish Water said the spate of wildfires in recent months, including several in the Dublin Mountains, had also affected supplies.
Another factor could make it even harder to deal with the current drought.
Dr Tom Collins, chairperson of government advisory body the Water Forum, said he feared the public was tired of bad news.
"There is probably an element of fatigue in the community because of Covid-19 and probably a sense that one crisis should be enough to cope with in a year," he said.
"I think people are not ready to cope with more dire warnings.
"The likelihood is that even a wet summer is unlikely to replenish the reservoirs, and there is no indication so far of a wet summer.
"I think the situation probably will get worse before it gets better."
Professor Fiona Regan, of Dublin City University's Water Institute, is also concerned the public's minds might be on other things.
"Water conservation is not a planning regulation, so we don't require rainwater harvesting or grey water recycling in our buildings," she said.
"If there isn't a requirement in law, it's hard to get people to see it as a requirement in practice.
"Suddenly, there's a requirement now because there's a water conservation order, but it needs to be a way of thinking at all times."