Why do you feel cool under a tree but not so under a tin shed on a sunny day?

The cooling effect experienced under a tree compared to a tin shed is primarily due to transpiration. While both provide shade by blocking direct solar radiation, trees actively cool the surrounding air through the evaporation of water from their leaves [t1, t2]. During transpiration, plants release water vapor through stomata; this process requires energy, which is absorbed from the immediate environment as latent heat of vaporization [c2, t3]. This 'evaporative cooling' significantly lowers the ambient temperature under the canopy [t3, t5]. In contrast, a tin shed is made of metal, which has high thermal conductivity and absorbs heat, often radiating it downwards, making the space underneath feel warmer. Thus, the tree acts as a natural evaporative cooler by converting liquid water into vapor, absorbing heat in the process [c1, t1].

Sources

1. [1] https://bag.leeds.ac.uk/projects/restoring-hardknott-forest/blogs-and-more/the-cooling-effects-of-tree-cover/
2. [2] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 10: Water in the Atmosphere > EVAPORATION AND CONDENSATION > p. 86
3. [3] Science-Class VII . NCERT(Revised ed 2025) > Chapter 7: Heat Transfer in Nature > 7.4 Water Cycle > p. 98