Answer:

The phenomenon of the sky turning purple-red before a storm is a fairly common optical phenomenon. It often occurs due to a combination of many meteorological and optical factors, and is often considered a warning sign of natural disasters forming and moving closer.

Sunlight passing through the atmosphere will be scattered in many different directions by small particles in the air (such as dust, water vapor, ...). Short-wavelength light (purple, blue) is scattered more strongly, while long-wavelength light (red, orange) is scattered less. When there is a lot of water vapor in the air (before a storm), red and orange light will easily penetrate thick layers of clouds, creating the characteristic color of the sky before a storm.

Before a storm arrives, the humidity in the air increases. Water vapor acts as a prism, causing sunlight to bend and scatter more, creating brilliant colors in the sky.

Dust particles and air pollution also contribute to light scattering, enhancing the color effect.