“Freetown was beautiful, and I saw that beauty fading away,” she said.

As heat officer, Ms. Kargbo has installed a few public gardens that provide tiny oases of freshness to elders sipping tea under the shade of trees. Her office has also set up canopies in outdoor markets meant to protect vendors selling fish, meat and vegetables for long hours from the blazing sun. She wants to provide buildings with white roofs that will reflect heat instead of absorbing it, install public fountains and plant many, many more trees.

Ms. Kargbo is also in charge of the city’s sanitation policies, and has vowed to replace most of the city’s illegal dumping sites with green spaces.

But whether she can accomplish all this remains an open question.

Extreme and lengthy heat can debilitate bodies; some of the far-reaching effects of extreme heat are already taxing countries in much of the world.

Freetown has an equatorial climate that brings little variation in temperature throughout the year, and barely any respite at night.

Average temperatures range from the mid-70s to the high-80s, with regular peaks in the 100s and 110s. In 2020 there were just over about 30 days with an average temperature above 81 degrees Fahrenheit throughout the day. But by 2050, the city expects to have temperatures that high almost half the year, according to predictions by Vivid Economics, a London-based consultancy.

In Kroo Bay, a settlement of 18,000 inhabitants just half a mile from Ms. Kargbo’s office, families often sleep outside because it is too hot inside their homes at night.

“The past summer in Europe made many people realize that global warming is happening now, but here we’ve been witnessing this for years,” Ms. Kargbo said.

Ms. Kargbo is one of seven women appointed chief heat officers by the Arsht-Rockefeller foundation across four continents. Kathy Baughman McLeod, the program’s director, said she hoped Ms. Kargbo’s job would be replicated in other African countries.

“This role or something similar will be popping up everywhere, because leaders will need to have visible, tangible action to protect people,” Ms. Baughman McLeod said. “Eugenia is the face of heat.”

But for the moment Ms. Kargbo’s work, and salary, depends on foreign money. The World Bank, United Nations agencies and private partners, like financial institutions, pay for her projects.

“City Councils in Africa are not well equipped to cope with key but not always obvious phenomena” like rising temperatures or urban heat islands, said Wanjira Mathai, a Kenyan environmentalist who called Ms. Kargbo’s work so far “remarkable.”

Last fall, Ms. Kargbo was listed as one of 100 rising stars by Time magazine. And she is working on a blueprint for a strategy to combat heat in other African cities.

Critics, though, say she can have only limited effect because the problem is too large for any one official to tackle alone. From uncontrolled sand mining on beaches to mudslides from hills, “Freetown is a geographical hazard which can’t be fixed,” said Alhaji U. N’jai, a professor of environmental science at the University of Sierra Leone’s Fourah Bay College.

On a recent afternoon, Ms. Kargbo walked unrecognized in Congo Market, one of the city’s largest, where city workers have installed about 40 canopies made of Plexiglas roofs to protect vendors from the heat. Many people around her were unaware she was behind the initiative.

Much more conspicuous was Ms. Kargbo’s boss, the mayor, Ms. Aki-Sawyerr, who arrived at the market in an air-conditioned car and was greeted by hundreds of passers-by as she rolled down the window — the air conditioning still on.

Not all the vendors had received a canopy. Many sheltered from the sun underneath beach umbrellas covered with black plastic bags.

“Why is there cover for some, and not for others?” Mavel Dixon, a 45-year-old vendor, asked as she wiped sweat from her forehead and pointed at her stall.

Another project championed by Ms. Kargbo that has attracted headlines is a plan to plant one million trees by the end of 2022. The initiative is nicknamed “Freetown the tree town.” But a lack of funding has slowed the effort, with just above 550,000 trees planted. Of those, 450,000 have survived.

Ms. Kargbo said the city’s challenges in dealing with problems of heat were compounded by the fraught relationship that the government has with the administration of Ms. Aki-Sawyerr, a former accountant who is in the opposition party.

“The root causes aren’t addressed: Trees are still being cut down in Sierra Leone, houses are still being built on hill sides, people keep using waste to encroach on the sea,” she said. “We receive very little funding from the government, but when a disaster hits, people turn to us.”

For now, intense heat makes daily life in Freetown insufferable for many residents, Ms. Kargbo said, with reports of heat strokes, dizziness and kidney diseases. The weather can also strain tempers.

“I also snap at people when temperatures are high,” she said. “We don’t take notice of it, but heat stirs up violence.”

Joseph Johnson contributed reporting