Emmanuel Himoonga paced his dry field, picking up stalks of maize that had been bleached almost to bone white.

The 61-year-old chief of Shakumbila, a mainly agricultural community of about 7,000 people roughly 70 miles west of Zambia’s capital, Lusaka, had seen droughts before.

But since 2010 they have been happening once every three to four years, instead of every five years. And, Himoonga said, he had never experienced a situation this bad before.

“When you look at the last rainy season, I have never seen anything like it in my life. Every crop we planted in these fields failed,” he said. “I have lost everything.”

Southern Africa is in the midst of its worst drought in at least a century, with 27 million people affected and 21 million children suffering from malnutrition, according to the World Food Programme (WFP).

An unprecedented El Niño-induced dry spell, which lasted almost two months from late January in the middle of what should have been the region’s rainy season, wiped out more than half the harvest in some countries.

Lesotho, Malawi, Namibia, Zambia and Zimbabwe have declared national disasters, while parts of Angola and Mozambique are also badly affected.

The region’s “lean season”, where small-scale farmers have to rely on stores of food to feed themselves until the next harvest, normally runs from around October to April. However, this year it started in August, said Eric Perdison, WFP’s southern Africa director.

“We have months ahead of us,” he told a media briefing in October. “It is also likely to further deepen the already high risk of chronic malnutrition.”

Perdison added: “If you look at rainfall patterns, if you look at drought patterns within the region, we cannot point to any other factor than climate change.”

Average temperatures have risen 0.45C in the last century in Zambia and the situation is set to get worse.

Zambia’s “very hot days”, where temperatures peak above 35C (95F), are forecast to rise from 110 days in 2000 to 155 days by 2080, according to a German government study.

This year, hunger is already stalking southern Africa. People in one hard-hit rural area of Mozambique are relying on just one meal a day of wild roots and fruit, said Antonella D’Aprile, WFP’s Mozambique country head.

Food donations from Zambia’s government and WFP, which has said it only has a fifth of the $370m (£285m) it needs to feed people across the region, have not been enough, said Himoonga.

“We cannot afford three meals a day and, me, I am better off,” said the chief, a father of 13. “You don’t want to imagine what is happening to my subjects. People are starving here and merely surviving by the grace of God.”

The drought is also pulling families apart. Agness Shikabala had not heard from her husband since August, when he left Shakumbila for Lusaka to look for work.

“I am worried that my children will start getting sick due to lack of food. Our barns are completely empty and then I can’t sell animals to feed the children without permission from my husband,” said the 23-year-old, who has six children to care for – three of her own and three from her husband’s previous marriage.

“My business involves buying agricultural products such as groundnuts and maize for resale in Lusaka. But here I am, totally stuck. There is nothing to buy and there is nothing to sell.”

Single and married women have resorted to selling sex to men who work at the nearby sugar plantation, Shikabala said.

“I love my husband so much and I respect him even if he has decided to desert us,” she said. “I am very hopeful that the rains will come next season and I am praying to God to keep me away from the temptation of sleeping with another man over a gallon of maize.”