Emergency repair crews were working to restore electricity in Ukraine’s Kyiv region after Russian strikes hit energy infrastructure, leaving many residents dealing with bitter cold and prolonged outages, according to officials and people living in the affected area.

In Boryspil, a town in the Kyiv region with a population of around 60,000, workers dismantled and rebuilt burned-out electrical systems as they raced to repair damage, with shifts running in snow from early morning until midnight. Yurii Bryzh, who leads the Boryspil regional department of private electricity provider DTEK, said the temperature was around -15 C (5 degrees F) and that the supply had been restored for about four hours a day.

Bryzh said the restoration is fragile because of what happens when power returns. He told The Associated Press that “when the power comes back on, people turn on all the electrical equipment that is available in the house” and that this collapses the system again.

In Kyiv, residents described nights in the dark, freezing apartments, and prolonged stretches without electricity. The hardships were acute as Kyiv Mayor Vitali Klitschko described the outages as the longest and broadest since Russia’s full-scale invasion of its neighbor almost four years ago, with some homes going without power for days.

Snow covered rooftops and ground across Kyiv, piled up near sidewalks, while the city’s nighttime streets were dark and towering apartment blocks showed no lights in windows, residents said. The rumble of generators was heard across the capital as temperatures remained well below freezing.

Among those coping without reliable electricity, a married couple of scientists, Mykhailo, 39, and Hanna, 43, said the temperature in the bedroom of their 5-year-old daughter Maria fell to -15 degrees C (5 degrees F). They said they keep warm with blankets and said they use all the blankets they have, with Hanna telling AP, “We have to use all the blankets we have in the house.”

The couple said they have a gas stove for cooking but huddle together at night under heavy blankets. They also take their daughter to work during the day because their premises have a generator while her kindergarten has no heating, and they said Christmas decorations still hang in the apartment, occasionally lit by flashlights.

Other residents described heating water and improvising warmth without electricity. Zinaida Hlyha, 76, said she heats water on a gas stove and puts it in bottles that she tucks into bed. She told AP she does not complain because Ukrainian soldiers on the roughly 1,000-kilometer (600-mile) front line have it worse, saying, “Of course it’s hard, but if you imagine what our guys in the trenches are going through now, you have to endure,” and “What can you do? This is war.”

Several residents also linked the cold to the risks of attacks. Tetiana Tatarenko said two of her sons are fighting in the war and that she became more fearful of Russia’s nighttime barrages after a Shahed drone hit an apartment building next door. She told AP, “It’s as if life in the house has stopped, that’s the feeling.”

Raisa Derhachova, an 89-year-old physicist who lives alone, said she sometimes plays the piano in what she called “this terrifying cold.” She told AP, “Of course, it’s hard to survive this. We survived World War II, and now this terrible war is upon us.”

Analysts said the scale of damage and the difficulty of replacing key components continue to slow recovery. Dennis Sakva, an energy sector analyst at Dragon Capital, said Russian barrages are aiming at power plants and large substations and that getting replacement equipment such as transformers can take months. He told AP, “There are two types of heroes in Ukraine. They are the military and energy workers.”

As freezing conditions have persisted for more than two weeks, AP reported that the temperature in Kyiv was minus 12 degrees Celsius (10 degrees Fahrenheit), with streets covered in ice. Kyiv had faced severe power shortages for days, and Klitschko said Monday night’s strikes caused the biggest electrical outage the city had faced so far.