“The majority of people have improved psoriasis in the summer,” says Dr. Orbai. That’s because the sun's UVB rays help slow the growth of affected skin cells. That said, in Dr. Kumthekar’s experience, about 10 percent of patients have worsened psoriasis in the summer. Dr. Orbai notes that inverse psoriasis, in particular, often becomes more irritated when the skin gets hot and sweaty. Also known as intertriginous psoriasis, inverse psoriasis typically shows up in skin folds, armpits, groin, and under the breasts. Hot and humid weather can increase rubbing and, consequently, irritation in affected areas. You can manage intertriginous psoriasis by staying dry, avoiding sweating, and bathing regularly (among other things, creams, treatment etc).