Half of Puerto Rico was without power on Wednesday as Tropical Storm Ernesto strengthened into a hurricane off the northern coast of the United States’ most populous overseas territory.

When heavy rains lashed the island around 4 p.m., nearly 84 percent of San Juan still had power.

But in Carolina, the municipality bordering the capital to the east, almost 80 percent of households were without electricity, Data from the energy supplier LUMA Energy.

In Mayaguez, Ernesto’s winds, gusting up to 120 km/h, were strong enough to plunge 76 percent of the west coast into darkness, with the percentage continuing to rise Wednesday afternoon. Blackouts on the south coast in Ponce, Puerto Rico’s second-largest city, and in Caguas, the central mountain municipality, followed a similar pattern, with no fewer than 67 percent of households without power.

Overall, the proportion of people in Puerto Rico without electricity fell by almost one percentage point to 50% on Wednesday afternoon. LUMA said in a opinion posted on X that its staff will “conduct on-site inspections once it is safe for our teams to be on-site to identify damage and begin repairs.”

LUMA, a private company that took over electricity sales from the state-owned utility in 2021, said its “priority is to restore supplies to critical consumers such as hospitals and water and sewage facilities.”

Atmospheric conditions that caused surface winds to blow in a different direction than winds at higher elevations weakened the hurricane and may have saved Puerto Rico from a major disaster, said Rosimar Rios-Berrios, a climate scientist at the National Center for Atmospheric Research in Boulder, Colorado.

“While it’s helpful in that we’re dealing with a relatively weak hurricane rather than a strong one, it can also bring very heavy rainfall,” Rios-Berrios, whose family still lives where she grew up in central Puerto Rico, said by phone Wednesday afternoon.

She predicted that the rains would ease by Thursday.

The storm follows a similar trajectory to Hurricane Fiona, which Puerto Rico hit in September 2022which left entire neighborhoods flooded with up to 76 centimeters of rain and left nearly a million households without power in an area with a population of about 3.3 million people.

While Rios-Berrios is hesitant to attribute any particular weather event to the long-term trend of rapid global warming, climate forecasts for this storm-prone part of the Caribbean showed an increased likelihood of heavy rains and a greater number of strong hurricanes.

“One effect of climate change could be the enormous rainfall,” she said. “Climate forecasts agree that as the oceans continue to warm, hurricanes could produce more rain, which could lead to catastrophic flooding.”

The latest blackout is likely to add to the political backlash against LUMA, which many Puerto Ricans blame for weekly, if not daily, power outages and the highest electricity prices in the United States.

The territory’s non-voting congressional delegate, Rep. Jenniffer González-Colón (R-R), won the gubernatorial primary this year for the ruling pro-state party, which campaigned on its opposition to the controversial deal that handed control of the power grid to LUMA, a joint venture between a Texas and Canadian energy company.

Last summer, more than 100,000 Puerto Rican households were left without power during a record-breaking heat wave. Another historic heat wave in June of this year led to blackouts that threatened to leave entire cities without electricity for over a month.

Rios-Berrios says it’s impossible not to worry when, as a scientist thousands of miles away, he’s watching basic infrastructure collapse under weather extremes and monitoring meteorological data in real time.

“I take all these cases very personally,” she said.

“Every time I see a case like Hurricane Ernesto – or, to be honest, every hurricane season, any time there’s even the slightest possibility that a hurricane could hit the island – I get very worried,” she said. “Not just for my family. The entire infrastructure of the island is so fragile, especially the power grid, and these storms are very powerful.”

However, the consequences of Ernesto could go far beyond power outages; severe flooding also poses a major risk.

Rios-Berrios said her family lives in a town in the central mountains and she fears landslides and flooding could block roads. She said she has been checking in regularly with relatives while they charge their phones and clear reception.

“I’ve heard about them,” she said. “They don’t have electricity.”

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