Why Does Pigmentation Become Worse During Summer? Hot Weather often causes pigmentation, tanning, and patchy skin tone in many people. If you want to know why pigmentation increases in summer, the biggest reason is strong ultraviolet rays from sunlight. The skin increases melanin production in summer as a protective response, https://sites.google.com/view/drnikitapatel/blog/why-does-skin-pigmentation-increase-in-summer