Executive summary

In Bhutan and across South Asia, increases in the frequency, intensity and duration of extreme heat events have become a climate, health and development challenge at once, affecting the overall wellbeing of communities. Rising global temperatures drive the hazard; rapid unplanned urbanisation and entrenched inequality determine who it harms.

Global mean temperature for January–August 2025 stood at 1.42 degree (±0.12°C) above pre-industrial levels, and each of the eleven years from 2015 to 2025 ranked among the eleven warmest in the 176-year observational record (WMO 2025). Heat-related deaths have risen 63 per cent since the 1990s, averaging 546,000 per year 20122021 (Romanello et al. 2025). By 2070, around 520 million people across South Asia could experience at least one month of dangerous heat each year, and under a 1. warming scenario, the region could lose 5.3 per cent of total working hours to heat stress by 2030 (World Bank 2026; ILO 2019).

Key findings

• Heat is already high in the southern lowlands
  Warming has been observed in Bhutan since the 1960s, with annual temperatures rising by just under 1 degree over the twentieth century and daily minimum temperatures rising faster than maxima (WBG and ADB 2021). Daily maximum temperatures already exceed 30 degrees in the south, and prolonged heat stress is expected at least once every five years in lower-altitude areas (GFDRR 2020; World Bank n.d.a). Pemagatshel records around 16 days above 30 degrees a year, followed by Sarpang at about nine, Samtse and Samdrup Jongkhar at about eight, and Zhemgang around seven (World Bank n.d.a).
• Heat intensifies and expands inland under every pathway
  The same southern dzongkhags that are hottest today gain the most additional hot days. Under SSP2–4.5 for 2040–2059, Pemagatshel rises to about 33 hot days a year and Sarpang to about 20; under SSP5–8.5, Pemagatshel reaches about 40 and Samdrup Jongkhar about 20, with Pemagatshel gaining roughly 25 additional hot days on the historical period (World Bank n.d.a). Northern high-altitude districts may warm by 2–3 degrees by mid-century and by more than 4–5 degrees in places by 2100, while valleys that were previously cooler, like Punakha, Wangdue Phodrang, Monggar, Trashigang and lower Thimphu and Paro, move into higher maximum temperatures, exposing populations not previously exposed to heat (ESCAP n.d.a; ESCAP 2026).
• The health burden is real but barely recorded:
  Observed clinical records of heat illness in Bhutan are sparse, and the national picture therefore rests on modelled estimates (Royal Government of Bhutan and UNDP Bhutan 2025; Chhetri, Zangpo and Gyeltshen 2024). For 2014–2023, the 2024 Lancet Countdown, as reported by WHO, shows adults over 65 exposed to around nine heatwave days a year, a rise of about 350 per cent on 1986–2005, and heat-related deaths among that group up about 340 per cent since the 1990s—an increase that would have been roughly 140 per cent without climate change. Heat exposure cost workers more than 19 million potential labour hours a year, equivalent to around US23.9 million in lost income, of which agriculture bore about 87 per cent (WHO 2025).
• The burden falls unevenly and disproportionately on women
  Because agriculture accounts for most heat-related income loss, outdoor rural workers are most at risk (WHO 2025). Almost 60 per cent of employed women work in agriculture, compared with over 34 per cent of men. Women perform about 71 per cent of unpaid household and care work. Access to climate-smart agriculture decision-making stands at 25.5 per cent for men against 11.7 per cent for women (NCWC and UNDP Bhutan 2020). Infants, adults over 65 and people with chronic cardiovascular disease or diabetes face higher physiological risk, while poorer households are least able to afford cooling, water storage or irrigation (WBG and ADB 2021; WHO 2025).
• Urban heat is a separate and growing pathway
  In Thimphu municipality, built-up area rose from 50.58 per cent to 67.57 per cent between 2001 and 2021 while vegetation fell from 44.76 per cent to 25.4 per cent. Hot urban heat island zones covered 11.83 per cent of the municipality in 2021 and very hot zones 4.22 per cent, projected to reach about 14.26 and 6.08 per cent by 2031 (Pasang et al. 2025). In Phuntsholing, modelled informality is around 31 per cent and air-conditioning penetration about 0.5 per cent, with heat-attributable deaths projected to rise from 1.8 to 4.5 and heat-related costs from USD 8.6 million to USD 11.2 million between 2025 and 2050 (“Heat Cost–Benefit Analysis tool”; Hera Now n.d.).
• Mandates exist but are not joined up
  National Adaptation Plan assigns the responsibility for assessing heatwave and heat-stress risk and for developing heat early warning, with the labour ministry and Khesar Gyalpo University of Medical Sciences as collaborating partners (Royal Government of Bhutan 2023). The Regulation on Occupational Health, Safety and Welfare 2022 requires acclimatisation time, work-rest schedules, drinking water and a heat stress prevention programme at hot workplaces (Department of Labour 2022). However, informal farm and care work, where much of the burden sits, falls outside it. No national or city heat action plan was found, and heat early warning remains undeveloped, unlike comparatively advanced flood and glacial lake outburst flood systems (Royal Government of Bhutan and UNDP Bhutan 2025; Royal Government of Bhutan 2023).

What Bhutan needs next to be heat resilient needs

The findings above identify where heat exposure and burden are concentrated. The next step is to strengthen how existing mandates are translated into coordinated, seasonal action. Responsibilities for heat-related risks already fall across health, labour, hydrometeorological services and human settlements. The key gap is coordination across these areas, supported by routine monitoring and agreed triggers for action. The report identifies four priorities.

• Establish heat-health surveillance and monitoring
  Observed clinical records of heat illness in Bhutan are sparse, so the national picture rests on modelled estimates rather than routine diagnosis. The Ministry of Health, working with the National Centre for Hydrology and Meteorology, can begin recording heat-related presentations at health facilities in the southern dzongkhags, and take forward the loss and damage indicators already proposed: hospital visits during and after events, days of lost productivity and cooling energy costs as a routine reporting system. Sex-disaggregated clinical and labour data would strengthen it further.
• Join existing mandates into a heat action plan
  Responsibilities for heat already exist across the Ministry of Health, the Department of Labour (under the 2022 occupational health regulation), hydrometeorology, disaster management and human settlements, but no instrument connects them. A national heat action plan, with city plans for southern border towns such as Phuntsholing where modelled informality is around 31 per cent and air-conditioning access close to zero, would convert assigned duties into coordinated seasonal action.
• Extend early warning from floods to heat
  Bhutan’s flood and glacial lake outburst flood early warning is comparatively advanced, with control-room systems and hydrometeorological modernisation already in place. Heat early warning, though a National Adaptation Plan activity, remains undeveloped. Building heat triggers and public health thresholds onto existing infrastructure is faster and cheaper than building a parallel system.
• Apply a differentiated vulnerability lens to heat-health action
  Heat exposure and its impacts vary across population groups, including by age, sex, occupation and income. Heat-health measures should therefore prioritise groups facing higher exposure or limited capacity to adapt, including older persons, outdoor and agricultural workers, and women engaged in unpaid care and agricultural work. This should include measures to identify and address heat-related illness that may not be captured through routine clinical surveillance. The 2022 occupational regulation applies to regulated workplaces; additional measures are needed to extend protection to informal agricultural and care work through health, labour and social protection systems.

The GHHIN South Asia Hub will help address these priorities in Bhutan by convening stakeholders, strengthening the regional evidence base, facilitating knowledge exchange, and building capacities for heat-health action. By connecting Nepal, Bhutan, Bangladesh, and India around shared priorities and solutions, the Hub will foster institutional collaboration and cross-country learning, supporting countries to advance sustained and anticipatory heat-health resilience across South Asia.