Climate of Bhutan

The climate of Bhutan is defined by the country's extraordinary vertical relief. Elevations rise from about 100 metres on the Indian border to more than 7,000 metres on the Tibetan frontier within a north–south span of roughly 170 kilometres — the steepest altitudinal gradient in South Asia. This compresses tropical, temperate and alpine conditions into a landmass smaller than Switzerland and produces three broad climatic belts layered by elevation. The Indian summer monsoon drives most of the country's rainfall, while westerly disturbances, orographic uplift and the rain shadow of the Great Himalayas shape strong regional contrasts. Bhutan's climate is also a live policy concern: the country is documented as net carbon-negative because of its forest cover, yet its high-altitude zones are warming faster than the global average and its glacial catchments are losing ice.

Climatic Zones

Bhutan is conventionally divided into three climatic belts corresponding to elevation, though boundaries are gradational and each district contains several of them.

Southern subtropical belt

The southern foothills — including Samtse, Sarpang, Samdrup Jongkhar and the lower parts of Chhukha and Dagana — lie between roughly 150 and 2,000 metres on the northern edge of the Duars Plain. Summers are hot and humid, with daytime highs reaching the high thirties Celsius in May and June. Winters are mild, frost is rare below 1,000 metres, and tropical or subtropical broadleaf forest dominates. Rainfall is the highest in the country. Figures reported by Encyclopaedia Britannica and regional climatology sources give annual totals of roughly 4,000 to 7,500 millimetres on the wettest foothill slopes, among the highest in South Asia, driven by orographic uplift as monsoon air from the Bay of Bengal strikes the Himalayan front.^[1]

Central temperate belt

The inner valleys of Paro, Thimphu, Punakha, Wangdue Phodrang, Trongsa, Bumthang, Mongar and Trashigang, generally between 2,000 and 4,000 metres, form the temperate belt where most of Bhutan's population lives. Summers are warm rather than hot, winters are cold and dry, and snow is common at higher elevations in December and January. Annual rainfall here is much lower than in the south — ICIMOD and World Bank climate profiles place the inner Himalayan valleys in the range of about 1,000 to 1,500 millimetres, with drier pockets such as Bumthang recording considerably less.^[2] Paro and Thimphu commonly see winter minima below freezing and summer highs in the mid-twenties.

Northern alpine belt

Above roughly 4,000 metres, running across Gasa, the Lunana and Lingshi regions, upper Paro and the highlands of Merak-Sakteng in Trashigang, the climate is alpine to arctic. Summers are short and cool, winters are long and severe, and permanent snow and glacier ice occupy the highest peaks from about 5,000 metres upward. Much of this belt lies in the rain shadow of the Great Himalayas, so annual precipitation — often falling as snow — is considerably lower than in the monsoon-exposed south, though exact values are poorly constrained because few weather stations operate at these elevations.

The Monsoon System

The dominant driver of Bhutan's climate is the Indian summer monsoon, which typically arrives in mid-June and withdraws by late September. According to Britannica and NCHM summaries, monsoon rainfall accounts for roughly 70 per cent of Bhutan's annual precipitation nationally, with higher shares — reported at 60 to 90 per cent depending on station and year — in specific catchments.^[1] April and May bring pre-monsoon thunderstorms and hail, which periodically destroy apple and maize crops in the central valleys. Winter, from December to February, is dry nationwide, broken only by occasional westerly disturbances that deliver snow to the temperate and alpine zones. Late-season tropical cyclones from the Bay of Bengal — most notably Aila in 2009 and Fani in 2019 — can also reach Bhutan as rain-bearing remnants.

Instrumental Record and NCHM

Systematic weather observation in Bhutan is a recent undertaking. The National Centre for Hydrology and Meteorology (NCHM), formally established as an autonomous agency in 2016 out of earlier departments, is the primary authority for meteorological data, hydrological monitoring and climate services. Most NCHM stations have continuous digital records dating from the 1990s, with some longer paper-based records at Paro, Thimphu and a handful of agricultural stations. Coverage at high elevation remains sparse, which constrains the detection of long-term trends in the alpine belt.^[3]

NCHM's published climate assessments show warming across all monitored stations since records began, with the strongest signal at higher elevations. The centre's 2019 climate projection report and subsequent bulletins indicate mean annual temperature increases of roughly 0.5 to 1.2 °C at mountain stations over the instrumental period, with faster warming since 1991, and project a further increase of about 2.1 to 2.4 °C by 2040–2069 under mid-range emissions scenarios.^[4] Because the instrumental baseline is short, these figures should be read alongside regional reconstructions from ICIMOD and the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report, which place Bhutan within a Hindu Kush Himalaya warming band that is rising faster than the global mean.^[5]

Glaciers and Glacial Lakes

Bhutan's cryosphere is concentrated in the Lunana region of Gasa and along the Great Himalayan watershed. The most widely cited ICIMOD inventory identified 677 glaciers and 2,674 glacial lakes in Bhutan, of which 24 were classified as potentially dangerous for glacial lake outburst floods (GLOFs).^[6] Most monitored glaciers are in retreat. Published rates include about 35 metres per year on the Raphstreng glacier from 1984 to 1998, rising to roughly 60 metres per year in the later part of that period, and up to 160 metres per year on the Luggye glacier between 1988 and 1993. ICIMOD's 2026 Hindu Kush Himalaya assessment concluded that the region's glaciers are losing ice at roughly double the rate of the pre-2000 period, though the report also notes that Bhutan remains among the more poorly monitored glacierised areas.^[7]

Glacial lake outburst floods

The most widely documented climatic hazard in Bhutan is the glacial lake outburst flood, in which a moraine- or ice-dammed lake breaches and releases a large volume of water down a mountain valley. On 7 October 1994, the moraine dam of Luggye Tsho in Lunana failed and released about 18 million cubic metres of water into the Pho Chhu, reaching Punakha in roughly seven hours. Contemporary assessments attribute around 21 deaths to the event, along with damage to Punakha Dzong, destruction of roughly a dozen houses, extensive crop and pasture losses, and the sweeping away of several bridges and chortens.^[8]

The adjacent Thorthormi and Raphstreng lakes have since been the focus of a long-running risk-reduction effort. A UNDP–GEF-backed artificial lowering project, implemented between 2008 and 2011, manually drained about 17 million cubic metres from Thorthormi and lowered its level by several metres; additional phases using siphon technology have been pursued by Bhutanese authorities with international partners.^[9] On 28 July 2015, Lemthang Tsho in north-western Bhutan burst after two days of heavy rain, releasing about 0.37 million cubic metres of water into the Mo Chhu, killing four horses and destroying bridges and trails along the upper Laya route but causing no human fatalities.^[10] Early-warning systems combining upstream water-level sensors, sirens and community drills have been installed along the Pho Chhu and other high-risk valleys, but coverage remains incomplete.

Extreme Weather and Disasters

Tropical cyclones from the Bay of Bengal occasionally reach Bhutan as rain-bearing systems. Cyclone Aila, which made landfall on the Bangladesh coast on 25 May 2009, delivered record rainfall to central and southern Bhutan. Government and NCHM assessments attributed 12 to 13 deaths in Bhutan to the storm, with infrastructure damage estimated at about Nu 722 million (roughly US$17 million at the time), washed-out roads across multiple dzongkhags, destruction of the Gasa hot springs, and river levels in Punakha and Wangdue that briefly exceeded the 1994 GLOF peaks.^[11] Cyclone Fani, as a remnant system in May 2019, killed at least eight people in Bhutan and damaged chortens, houses and crops, mainly in the south.^[12]

Flash floods have become, in the phrasing of one regional climate journal, the "dangerous new normal" for Bhutan, with high-intensity rainfall events increasingly causing localised mudflows, landslides and bridge failures during the monsoon.^[13] The country's institutional response is coordinated through the Department of Disaster Management under the Ministry of Home Affairs, operating under the Disaster Management Act 2013, which defines responsibilities for preparedness, response and recovery at national and dzongkhag level.

Observed Impacts

Climate change impacts reported by NCHM, the Ministry of Agriculture and Livestock, UNDP and academic researchers cover several sectors.

Agricultural shifts. Apple-growing elevations in Paro and Thimphu have crept upslope as warmer winters reduce chill hours; cardamom zones in the south have shifted, and rice and potato calendars have become harder for farmers to plan. Pre-monsoon hail events are frequently cited in Kuensel reporting as a recurring cause of crop loss.
Water security. Villages across multiple dzongkhags have reported the drying of traditional springs — known colloquially in Dzongkha contexts as chhu nyimey (disappearing water) — which has become a recognised focus of adaptation projects run by the Bhutan Trust Fund for Environmental Conservation, UNDP and the Adaptation Fund in districts including Paro, Dagana and Tsirang.^[14]
Forest fires. NCHM and the Department of Forests and Park Services have recorded an increasing frequency of dry-season forest fires, most commonly in pine stands around Thimphu, Wangdue and Trashigang.
Hydropower variability. Because more than 99 per cent of Bhutan's installed generation is run-of-river hydropower, drier winters and changing glacier-melt regimes translate directly into seasonal revenue volatility — an issue flagged by the Ministry of Finance and in IMF Article IV reports.

Carbon-Negative Status

Bhutan is one of a very small number of states documented as net carbon-negative: its forests sequester more carbon dioxide than the economy emits. The 2008 Constitution requires that at least 60 per cent of the country's land area remain under forest cover in perpetuity, and official inventories place actual forest cover above 70 per cent, with figures around 71 per cent in the 2016 Land Use and Land Cover assessment and higher in some later reports.^[15] In its Intended Nationally Determined Contribution submitted to the UNFCCC in September 2015, Bhutan committed to remain carbon-neutral, reaffirming this pledge in subsequent submissions under the Paris Agreement. Reaching that target depends on continued forest protection, limits on vehicle emissions and the further expansion of clean electricity.

Independent analysts have noted that the carbon-negative framing, while defensible under the current inventory methodology, masks embedded questions — including the climate footprint of imported fuel and construction materials, rising vehicle numbers in Thimphu, and the hydropower sector's dependence on glacier- and monsoon-fed flows that climate change itself threatens.

Uncertainty and Data Gaps

Several qualifications should be kept in mind when reading any single temperature or rainfall figure for Bhutan.

The instrumental network is short — mostly under 35 years at digital resolution — and concentrated in valley floors, so trend estimates at high elevations rely heavily on modelling and regional proxies.
ICIMOD's 2026 Hindu Kush Himalaya assessment explicitly lists Bhutan among the region's less-monitored glacierised areas, meaning ice-loss estimates carry wider uncertainty bands than for the central Himalaya.^[7]
Rainfall figures for the southern foothills vary considerably between sources, reflecting both real orographic gradients and sparse gauging on the Indian border.
Coverage of slow-onset impacts such as spring drying is largely confined to project reports and academic studies; comprehensive national monitoring is still being developed.