MEXICO CITY — Mexican officials imposed severe, monthslong cuts to Mexico City’s water supply at midnight Friday, acting just a month after initial restrictions were ordered as drought dries the capital’s reservoirs.

The Mexican National Water Commission and mayor announced the moves at a news conference, but officials did not report the cuts on social media until just four hours before they took effect.

Abnormally low rain has dropped the Cutzamala system — a network of three reservoirs serving over 20 million residents in the Valley of Mexico — to historic seasonal lows. The system is 44% lower than it should be at this time of the year.

Officials began restricting water from Cutzamala by roughly 8% on Oct. 17. Friday’s cuts are much more drastic, representing a further 25% of the system’s total flow. Twelve boroughs, mostly in the west of the city, can expect lower water pressure until the restrictions lift, officials said.

Officials did not specify when that would be, saying only that restrictions would stand for “the next few months.” They noted the rainy season — which at normal levels of precipitation would replenish the city’s water — won’t start until around May.

Mexico has never before announced such stringent or long-running restrictions to the city’s water because of drought. The city’s residents have suffered worse cuts in the past, but only because of strikes or repairs, all of which ended within days.

Officials said El Niño and heat waves caused the recent falloff in rain, but added that drought conditions have been intensifying the past four years and gradually lowering reservoir levels. Studies have shown climate change creates stronger El Niño patterns that bring periods of decreased rain.

“The country has been subjected to extreme weather phenomena, and the Cutzamala System is no exception,” said the water commission’s head, Germán Arturo Martínez Santoyo.

Mexico as a whole had 25% less rainfall than expected this year, compared to averages from the past three decades. More than three-quarters of the country is experiencing drought, the commission reported, while 93% of the Valley of Mexico itself is in drought, the country’s chief meteorological expert said.

Officials announced three new water wells and improvements to 58 existing wells, despite experts warning that the city’s groundwater is already severely depleted. The commission also said it would continue work on a new water treatment plant at the Madin reservoir, just northwest of Mexico City.

Rafael Carmona Paredes, the capital’s chief water official, urged people “to adopt new habits” to ensure the city does not run out of water.

“The problem we face requires that, as citizens, we take responsibility,” Paredes said.