TIL BDR GHALLEY | Thimphu
Bhutan recorded its warmest year on record in 2025, while three new national climate assessments show that rising temperatures, shrinking glaciers and increasingly erratic rainfall are reshaping the country’s water resources and heightening risks to infrastructure, agriculture and disaster preparedness.
The National Centre for Hydrology and Meteorology (NCHM) released State of the Climate 2025, Climate Atlas of Bhutan (1996–2025): Climatology of Temperature and Rainfall, and the country’s first Inventory of Freshwater Lakes in Bhutan.
Together, the three publications provide the most comprehensive scientific picture yet of Bhutan’s climate, freshwater resources and long-term weather patterns, establishing national baselines to support climate adaptation, disaster risk reduction and development planning.
According to State of the Climate 2025, Bhutan’s annual average temperature reached its highest level since records began, surpassing the previous record set in 2024.
The national average maximum temperature reached 23.33 degrees Celsius, while the annual average minimum temperature was 12.84 degrees Celsius, making 2025 the warmest year recorded in the country.
The assessment says Bhutan’s warming trend is more pronounced than the global average. While the World Meteorological Organization recorded global near-surface temperatures in 2025 at about 1.44 degrees Celsius above the pre-industrial baseline, Bhutan experienced another record-breaking year, continuing a pattern of rising temperatures.
Although the country received 1,742.91 millimetres of average annual rainfall—within the normal range—the assessment shows rainfall distribution became increasingly uneven throughout the year.
The summer monsoon from June to September remained drier than normal, with cumulative rainfall below the long-term average for most of the season despite brief periods of heavier rainfall during mid-August and early September.
In contrast, an intense and prolonged rainfall event in October, triggered by a low-pressure system originating over the Bay of Bengal, caused widespread damage to roads, bridges and hydropower infrastructure, highlighting how rainfall is becoming increasingly concentrated in extreme events rather than being evenly distributed throughout the year.
mong individual weather observations, Phuentsholing recorded the country’s highest annual rainfall at 5,402.31 millimetres and the highest 24-hour rainfall of 385 millimetres. Gasa experienced the highest number of rainy days with 202 days, while Haa recorded the country’s lowest daily minimum temperature of 4.44 degrees Celsius and experienced 141 days with temperatures at or below freezing.
The assessment also documents continued changes in Bhutan’s cryosphere. Long-term monitoring shows benchmark glaciers at Gangju La, Thana and Shodug continue to lose ice mass, confirming a sustained negative glacier mass balance. Bhutan currently has 17 Potentially Dangerous Glacial Lakes (PDGLs) that continue to pose a risk of glacial lake outburst floods to downstream communities and infrastructure.
Officials NCHM said the latest inventory identified 50 newly formed glacial lakes that now meet the scientific criteria for classification as lakes. They also said 27 glacial lakes documented in an earlier inventory of about 700 glacial lakes have disappeared, illustrating the rapid changes taking place in Bhutan’s high mountain environment as glaciers continue to evolve.
The broader picture is reinforced by the Climate Atlas of Bhutan (1996–2025), which compiles three decades of observations from 125 temperature stations and 98 rainfall stations to produce Bhutan’s first nationally consistent climatological baseline.
The atlas maps long-term temperature and rainfall patterns across Bhutan’s diverse landscape, where elevations range from about 160 metres to more than 7,000 metres above sea level. It shows temperatures decreasing steadily with elevation, while rainfall varies sharply because of the country’s rugged terrain and the influence of the southwest monsoon.
It also shows that approximately 73 percent of Bhutan’s annual rainfall occurs during the summer monsoon, while winter contributes only about one percent. The atlas is intended to strengthen planning in agriculture, hydropower, water resources, infrastructure development and disaster risk reduction by providing location-specific climate information.
Meanwhile, the Inventory of Freshwater Lakes in Bhutan establishes the country’s first comprehensive national database of freshwater mountain lakes, filling a longstanding information gap in Bhutan’s water resources.
Using Sentinel-2 satellite imagery processed through Google Earth Engine and verified through field surveys, researchers identified 2,391 freshwater lakes across nine major river basins and subbasins.
Together, the lakes cover 55.56 square kilometres, representing approximately 0.144 percent of Bhutan’s land area.
The Puna Tsang Chu sub-basin contains the largest concentration, with 769 lakes covering 19.22 square kilometres, while the Nyera Ama sub-basin has the fewest, with 13 lakes covering 0.11 square kilometres.
The inventory estimates that Bhutan generates about 70,576 cubic hectometres of freshwater annually and has an annual per capita freshwater availability of approximately 94,500 cubic metres, making it one of South Asia’s most water-rich countries.
Despite this abundance, only about one percent of the freshwater generated annually is used within Bhutan because of the country’s rugged terrain and limited water infrastructure, while approximately 99 percent flows downstream into India. Of the water used domestically, 86 percent is consumed by agriculture, 9.5 percent by industry and 4.5 percent by households.
The inventory also establishes a scientific baseline for monitoring future changes in lake extent resulting from climate change, land-use change and other environmental pressures.
Deputy Chief Statistical Officer with meteorological services division Ugyen Chophel said the climate assessments should serve as a basis for preparedness across government agencies, sectors and communities.
“We have to take a precautionary approach. Don’t wait for a deterministic forecast before taking action,” he said, noting that scientific forecasts always involve uncertainty. He said it remains too early to determine whether the impacts of upcoming weather conditions will be severe or moderate, but current rainfall and temperature patterns warrant close monitoring.
“When it comes to risk management, it is very important that we always consider the worst-case scenario. Our ultimate objective is to save lives and property,” he said.
Ugyen Chophel urged people to assess risks within their own communities, saying residents are often the best judges of local hazards because they understand the vulnerabilities of their surroundings. He also encouraged the public to stay updated through official weather forecasts and advisories issued by NCHM.
“If we forecast rain and it doesn’t happen, that is acceptable. But if we fail to issue an advisory and a hazardous event occurs, that is what we want to avoid,” he said.
Taken together, the three climate assessments show that while Bhutan remains rich in freshwater resources, rising temperatures, continued glacier retreat and increasingly variable rainfall are altering the natural systems that support water security, hydropower generation, agriculture and disaster resilience. The datasets are expected to strengthen evidence-based policymaking, climate adaptation planning and long-term environmental monitoring as Bhutan responds to the impacts of climate change.
