Due to architectural restraints and strict regulations to preserve the museum's art, there is very little air conditioning in the Vatican Museums. There are a substantial number of windows open during the warmer months to allow a breeze inside, along with some portable air conditioning units.

The Vatican Museums are only partially air-conditioned, which can make summer visits quite challenging. Due to the historic architecture and strict regulations to protect 500-year-old frescoes and tapestries, central HVAC systems are not installed in the vast majority of the galleries. Areas that are air-conditioned include the booking office, the gift shops, the Sistine Chapel (to protect the frescoes from humidity), and the newer Raphael Rooms sections. However, the long hallways and many of the sculpture galleries rely on open windows and portable fans to circulate air. In 2026, the museums have expanded their "night openings" until 10 PM on Fridays during the summer to allow guests to explore in cooler temperatures. If visiting during July or August, it is highly recommended to book the earliest possible 8 AM entry to beat the peak midday heat. Standard dress codes (covered shoulders and knees) are strictly enforced even in the hottest months, so wearing breathable, lightweight fabrics is essential for comfort while navigating the mostly non-climate-controlled halls.