No, it is not advised to forego SPF on cloudy days. Even when the sun is not visibly bright or direct, ultraviolet rays can penetrate clouds and cause skin injury.
Even on cloudy days, a significant quantity of UVA and UVB rays can still reach the Earth's surface. These rays cause premature aging.
Even on cloudy days, surfaces such as water, sand, and snow can reflect UV radiation. This reflection can intensify UV exposure, increasing the risk of sunburns.
UV damage is cumulative, which means that its effects accumulate over time. Protecting your skin consistently, even on cloudy days, helps prevent long-term effect.
Your epidermis is exposed to UV rays whether you are indoors near a window or outdoors, necessitating the use of SPF.
Regardless of the weather, it is recommended to use a broad-spectrum sunscreen with an SPF of 30 or higher for optimal protection.
Apply it liberally to all exposed skin areas, even on cloudy days, and reapply it every two hours, particularly if you're spending extended time outdoors.