Flash floods ripped through the western border province of Farah on Tuesday, washing away 21 people, while three more were killed when a hail storm caused their house to collapse.

"The flood was strong, it destroyed my farm, it destroyed everything... all the lands were flooded away," Nasrullah, a 50-year-old farmer, told AFP.

"In my sixty years of life I had never seen such wind, rain, and storm," said another farmer, Mohammad Ibrahim. He said the storm was so strong it "threw the fences 30-35 meters away" and blew away everything made of wood.

The district governor, Mohammed Sadeq Jehadmal, told AFP that 50 houses and 60 shops were damaged, while "between 2,000 up to 2,500 solar panels were destroyed".

Further east, six people were killed in Helmand province, including a child struck by lightning, and nine in Kandahar province.

Officials said the deadly downpours may however help improve long-term drought conditions in several provinces, including flood-hit Farah.

"It's constantly raining and snowing in most of the provinces, which has reduced the drought," said Abdullah Jan Sayeq, spokesman for Afghanistan's National Disaster Management Authority.

"This will enrich the water infrastructure. Agriculture will be improved and will have positive effects on livestock."

Afghanistan is among the poorest countries in the world after decades of war and is particularly exposed to the effects of climate change, which scientists say is spurring extreme weather.

It is ranked as the country sixth most vulnerable to climate change.

Drought, floods, land degradation and declining agricultural productivity are key threats, according to the UN.

Flash floods in May last year killed hundreds and swamped swaths of agricultural land in Afghanistan, where 80 percent of people depend on farming to survive.