Urban Morphology Shapes the Magnitude and Timing of Peak Heat Stress: Diurnal Thermal Lag and Seasonal Trade‐Offs in Srinagar, a High‐Altitude Himalayan City

ABSTRACT The timing of peak pedestrian‐level thermal stress is strongly influenced by urban morphology—displaced several hours beyond peak solar forcing by street canyon geometry—yet this temporal dimension of urban heat exposure remains unquantified in high‐altitude Himalayan cities despite rapid urbanisation across the region. This study examines how urban morphology influences the magnitude and timing of thermal exposure in Srinagar (1585 m a.s.l.), a high‐altitude Himalayan city with sharply contrasting historic‐core and planned‐colony fabrics. Height‐to‐Width ratio (H/W) and Sky View Factor (SVF) were derived city‐wide from a terrain‐corrected normalised digital surface model, substantially reducing hillside‐conflation bias in this topographically complex mountain valley setting. Two independent ENVI‐met V5 simulations—a planned‐colony domain ( Bemina ; H/W ≈ 0.4, SVF ≈ 0.75) and a historic‐core domain ( Shehr‐e‐Khas ; H/W ≈ 1.2, SVF ≈ 0.42) —were executed under identical 1 July clear‐sky forcing and evaluated against the long‐term IMD Srinagar Airport climatological envelope (2000–2024), confirming regional meteorological consistency. An indicative 3–3.5‐h diurnal thermal lag was observed in both domains, aligning with established UHI hysteresis values, while the novel comparative result was the stronger heat‐exposure penalty in the planned colony: higher peak temperatures, longer UTCI strong‐heat‐stress duration and greater afternoon exposure. Planned‐colony peak temperatures exceeded the historic core by approximately 1°C–1.5°C, while UTCI strong‐heat‐stress conditions persisted for 3.5–4 h—nearly twice the historic‐core duration—coinciding with peak afternoon outdoor activity. A GIS‐based winter solar‐access analysis further reveals a seasonal trade‐off: the same morphological openness creating summer thermal vulnerability simultaneously confers winter solar‐access benefits under winter insolation geometry. Together, these findings provide a temporal thermal assessment framework and morphology‐based planning insights that may inform climate‐responsive urban expansion in morphologically similar high‐altitude cities, while broader applicability requires validation across additional urban settings.