The previous summer, when he informed the community of record high temperatures amid an ongoing heat wave, there was little to be done to protect crops already in the ground. And last November, when heavy rains fell during what is usually the dry season, he could only describe the extent of the flooding that soaked and destroyed a hectare of maize.

Sitting at a wooden table in the village community hall in late March, below a portrait of revolutionary leader Ho Chi Minh, Nguyen, a congenial 58-year-old wearing a black sports jacket and baseball cap, explains that his duties as an elected official now include “teaching about climate risk”. He knows that global weather systems are shifting – the past year’s temperature extremes and unusual downpours in Vietnam are the result of a combination of climate change and El Nino – and that this has immediate, some­times devastating, effects on the 192 households in his village, mostly farming families in concrete homes with palm-frond roofs.

Vietnam is long and skinny, like an elongated “S” hug­ging the South China Sea, and it spans multiple climate zones. It has strong textile, footwear and electronics industries, but the country is also an important exporter of agricultural products including coffee, rice, cashew nuts, pepper and cassava starch. While farmers in the mountain­ous north worry about drought and erosion, those in the Mekong Delta region are concerned about rising sea levels and saltwater intrusion into rice paddies.

Across South and East Asia, an area home to roughly half the world’s population, the alternation between a relatively dry winter and a wet summer is controlled by monsoon winds. The speed and direction of these winds is driven by the differ­ence between land and sea temper­a­tures.

In spring and summer, as the Asian land mass warms more quickly than the surrounding seawater, winds blow inland from the Indian Ocean, bring­ing rain. But today, as average global temperatures increase, this gradient is in flux, altering the timing, intensity and predictability of monsoon rains. In a destabilised climate system, temper­ature extremes are more common, as are freak rain events such as the November 2015 flooding in Ma Village.

Over many centuries, Vietnam’s farmers carefully chose their crops and planting times to suit the rhythm of the monsoons. In the mountainous northern province of Yen Bai, where Ma Village is located, there are typically two rice seasons, with the first planting in February and the second in late June. Now “the rainfall pattern has changed”, says Nguyen.

Recently the rains have been inconsistent, arriving up to several weeks later – meaning, in some years, a prolonged spring drought that imperils the first harvest. Meanwhile, summer rains have fallen on fewer days, but the rain that comes has generally been heavier.

When rains come earlier or later than expected, it inter­feres with plant growth cycles, which require moisture at precise stages. Crops are also more vulnerable to temper­ature extremes at certain times.

On a late March morning, Lam Thi Minh, a 47-year-old farmer wearing rubber boots and a floppy cloth hat, is pulling weeds in a lowland rice paddy.

“Normally by this time there should be rain, but not yet this year,” she says, sounding worried. She recalls that two or three years ago, very dry weather during the delicate heading stage of rice growth interfered with the plants’ development. Her rice yields decreased by about 30 per cent, she says.

Another farmer, 41-year-old Tran Trung Kien, strolling through his pomelo orchard with clucking chickens roam­ing underfoot, voices a similar concern.

“The fruit setting will be affected without rain,” he says, referring to the growth stage after pollination that deter­mines whether a tree produces fruit.

Last year, rains were delayed by more than a month, bringing another problem: the long dry spell allowed a new pest to thrive, affecting the spring cassava harvest. Red mites “prefer dry conditions”, Nguyen says. “The mites only died when the rains finally appeared.” That season, cassava yields fell by nearly half, he says. Another factor that may have depressed yields is erosion, exacerbated by intense summer downpours.

Ma Village is beginning to test simple ways of adapting to climate change, in partnership with the International Centre for Tropical Agriculture (CIAT), a global research institute with regional offices in Hanoi. On a steep hillside plot, Nguyen Duy Nhiem, a CIAT researcher who has lived in the village for six months (he is not directly related to the village chief), is building narrow earth mounds at regular intervals, on which grass will be planted. The idea is that grassy strips crisscrossing the cassava field will help limit erosion by trapping dirt.

At the bottom of the field, Nguyen has helped construct a ditch lined with plastic to see how much soil is eroded. Over the next three years, his team will monitor trapped sediment and cassava yields to test whether redistributing retained topsoil on the field improves harvests.

Back at the CIAT office in Hanoi, soil scientist Bui Vinh Le and his team will measure soil from the same fields for the relative levels of carbon, nitrogen, phosphorous and other elements that improve soil productivity. The effects of recent changes in the monsoons – fewer days of rain, but more dramatic summer rainfall – are amplified by geo­graphy, in this case the mountainous landscape, he says.

“There are still normal years that allow farmers to follow their [previous] seasonal plans, but there are abnormal years ... this abnormality is hard to predict or be foreseen by farmers,” says Bui.

The Ministry of Agriculture and Rural Development in Hanoi now takes climate change into account when devis­ing central plans for agriculture.

“Forecasting is important – we have to be flexible,” says Pham Tien Duy, vice-chair­man for agriculture of Mau Dong commune (a commune is the administrative level above a village). “I try to see if an area will have enough water or not, and if the forecast is dry, I advise changing from rice to maize for a season,” since maize is less water intensive. Pham says forecasts can also help inform decisions about when and whether to test drought-tolerant and cold-tolerant rice varieties.

The winter’s cold snap also stunned officials in a district near Ma Village. In January, unprecedented snow fell on mountains above 900 metres. Doan Van Thuy, vice-chair­man for agriculture in the Yan Ten district of Yen Bai province, reports that at least 60 cows and buffalo died in his ward, and 300 hectares of rice seedlings were destroyed.

“I never saw snow before,” he says.

MIT Technology Review