The Eiffel Tower can grow up to 6 inches taller during the summer.

The Eiffel Tower is constructed from puddled iron, a material highly sensitive to temperature changes. When the iron atoms are heated by the sun, they gain kinetic energy and take up more space, a physical phenomenon known as thermal expansion. According to the Societe d'Exploitation de la Tour Eiffel, this expansion can cause the tower to grow by up to 15 centimeters (approximately 6 inches) during peak summer heat.This expansion is not just vertical. Because the sun only hits one side of the tower at a time, that side expands more than the shaded side, causing the top of the tower to tilt away from the sun. This solar tilt can move the summit by as much as 7 inches (18 centimeters) in a single day. The tower's height also fluctuates based on the ambient temperature and the duration of sunlight exposure.Gustave Eiffel and his engineers accounted for these movements during the design phase in the late 1880s. The structure's lattice design and the specific properties of the iron allow it to withstand these constant shifts without suffering structural damage. The tower essentially 'breathes' with the seasons, expanding in the heat of July and contracting during the cold of January. This flexibility is a key reason why the monument has remained stable since its completion in 1889.