_(i) Urban greening._ Based on review of existing Heat Action Plans and urban greening interventions, we established that a medium-ambition investment involves increasing the city's total tree canopy area by 10%, while a high-ambition investment entails a 30% increase. For example, if the city currently has a 10% tree canopy coverage, the medium-ambition plan aims to raise it to 20%, and the high-ambition plan seeks to raise it to 40% within the city boundaries. It was assumed that two trees can be planted on a 10 x 10-meter square. The unit cost for each additional tree planted was US$ 2.50. Maintenance cost per newly planted tree was estimated at US$ 5 per year based on US reference values with PPP conversion applied (Vogt et al, 2015).

(ii) _Early warning systems_ . Heat health early warning systems are designed to convert weather forecasts of potentially harmful conditions into alerts that prompt individuals and institutions to take action to prevent heat-related illnesses and deaths. In our study, we used international benchmarks to estimate the initial setup and annual operating costs of implementing such a system in a large Indian city. The startup costs were estimated at US$ 150,000, using data from the U.S. city of Philadelphia, adjusted for PPP and inflation (Ebi et al., ibid).

We based the operating costs on a model for managing heatwave alert systems, with cost references from Madrid, Spain. Rather than relying on a fixed annual cost, as done in Toloo et al. (2013), we used a per-heatwave-day cost approach, using data from Chiabai et al. 2018. The operating costs, converted from Spain to India using the PPP index, were approximately US$ 1,800 per heatwave day.

Additionally, some actions, such as operating the public heat advisory service (‘Heatline’) and deploying extra Emergency Medical Service (EMS) crews, incur direct costs, primarily in the form of additional wages. Based on Ebi et al. (2004), we estimated these wage costs to be approximately US$ 4,750 per day, with around 40% allocated to EMS crews, up to 30% for maintaining the Heatline during heatwaves, and the remainder for other medical assistance.

(iii) _Working hours shift_ . One of the most straightforward but challenging adaptation measures to implement is shifting working hours to an "early morning" and "late afternoon" schedule. This change is particularly important for workers engaged in intense outdoor physical activities, who are most affected by excessive heat, leading to reduced productivity, especially during the middle of the day. Assuming current working hours are from 8 AM to 6 PM, including a one-hour break at 1 PM, the proposed adjustment involves shifting to a schedule of 6 AM to 11 AM and 3 PM to 7 PM for 25% (medium-ambition package) and 50% (high-ambition package) of outdoor workers. This shift aims to reduce the loss of working hours due to intense mid-day heat. Although this midday break policy effectively reduces heat-related issues, it can be challenging for workers who have long commutes between home and work. However, the United Arab Emirates has successfully addressed this concern by implementing a break from 12:30 to 3:00 PM from June to September (MoHRE, n.d.).

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