smell of chlorine

Lightning strikes produce Ozone, hence the characteristic smell after lightning storms

Ozone, the triple oxygen molecule that acts like a protective stratospheric blanket against ultraviolet rays, is created in nature by lightning. When it strikes, the lightning cracks oxygen molecules in the atmosphere into radicals which reform into ozone. The smell of ozone is very sharp, often described as similar to that of chlorine. This is why you get that “clean” smell sensation after a thunderstorm.