Under blazing skies at a tea plantation in India’s northeastern state of Assam, worker Kamini Kurmi wears an umbrella fastened over her head to keep her hands free to pluck delicate leaves from the bushes.

“When it’s really hot, my head spins and my heart begins to beat very fast,” said Kurmi, one of the many women employed for their dextrous fingers, instead of machines that harvest most conventional crops within a matter of days.

Weather extremes are shrivelling harvests on India’s tea plantations, endangering the future of an industry renowned for beverages as refreshing as the state of Assam and the adjoining hill station of Darjeeling in West Bengal state, while reshaping a global trade estimated at more than $10bn a year.

“Shifts in temperature and rainfall patterns are no longer occasional anomalies; they are the new normal,” said Rupanjali Deb Baruah, a scientist at the Tea Research Association.

As changing patterns reduce yields and stall output, rising domestic consumption in India is expected to shrink exports from the world’s second-largest tea producer.

While output stagnates in other key producers such as Kenya and Sri Lanka, declining Indian exports, which made up 12 percent of global trade last year, could boost prices.

Tea prices at Indian auctions have grown by just 4.8 percent a year for three decades, far behind the 10 percent achieved by staples such as wheat and rice.

The mildly warm, humid conditions crucial for Assam’s tea-growing districts are increasingly being disrupted by lengthy dry spells and sudden, intense rains.

Such weather not only helps pests breed, but also forces estate owners to turn to the rarely used practice of irrigating plantations, said Mritunjay Jalan, the owner of an 82-year-old tea estate in Assam’s Tinsukia district.

Rainfall there has dropped by more than 250mm (10 inches) between 1921 and 2024, while minimum temperatures have risen by 1.2 degrees Celsius (2.2 degrees Fahrenheit), the Tea Research Association says.

The monsoon, Assam’s key source of rain, as summer and winter showers have nearly disappeared, brought rainfall this season that was 38 percent below average.

That has helped to shorten the peak output season to just a few months, narrowing the harvesting window, said senior tea planter Prabhat Bezboruah.

Patchy rains bring more frequent pest infestations, leaving tea leaves discoloured, blotched brown, and sometimes riddled with tiny holes.

These measures, in turn, add to costs, which are already rising at 8 to 9 percent a year, driven up by higher wages and prices of fertiliser, said Hemant Bangur, chairman of the leading industry body, the Indian Tea Association.

Planters say government incentives are insufficient to spur replanting, crucial in Assam, where many colonial-era tea bushes yield less and lose resilience to weather as they age beyond the usual productive span of 40 to 50 years.

India’s tea industry has flourished for nearly 200 years, but its share of global trade could fall below the 2024 figure of 12 percent, as the increasing prosperity of a growing population boosts demand at home.

Domestic consumption jumped 23 percent over the past decade to 1.2 million tonnes, far outpacing production growth of 6.3 percent, the Indian Tea Association says.

While exports of quality tea have shrunk in recent years, India’s imports have grown, nearly doubling in 2024 to a record 45,300 tonnes.

That adds expense for overseas buyers, said executives of India’s leading merchants, at a time when global competitors such as Kenya face similar problems.