Medically reviewed by Clare Wightman MS, PAC, Dermatology, Medical Research — Written by Sasha Santhakumar
A person can still get sunburn on a cloudy day. A high percentage of ultraviolet (UV) light emitted by the sun penetrates through clouds. People should still try to protect their skin as they would on a sunny day.
The sun emits UV light, which can penetrate the skin’s outer layer and cause changes resulting in burns. Sunburn may speed up the rate at which the skin ages. There are three types of UV light: UVA, UVB, and UVC. Each has different wavelengths and different consequences for the skin.
A person can take precautions to prevent sunburn by reducing their exposure to UV light and protecting their skin.
This article will explore whether a person can get sunburn on a cloudy day, what the symptoms of sunburn are, and how a person can protect against exposure. It will also explore the risk factors for sunburn.
Even on cloudy days, the sun still emits UV light, which penetrates clouds and can result in sunburn. Over 90% of UV rays can pass through a light cloud cover and cause sunburn.
UV levels tend to be highest under cloudless skies, and cloud cover generally reduces a person’s exposure. However, light clouds offer little protection and even enhance UV levels due to an effect called scattering.
Many surfaces also reflect UV radiation, which adds to the overall UV levels a person experiences:
- grass, soil, or water reflect less than 10% of UV radiation
- sands reflects about 15%
- seafoam reflects about 25%
- fresh snow almost doubles a person’s UV exposure
Types of UV radiation
There are three different types of UV light, which have varying wavelengths. They are:
- Ultraviolet A (UVA): This type of light has a wavelength of 315–399 nanometers (nm) and is associated with skin aging.
- Ultraviolet B (UVB): This type has a wavelength of 280–314 nm and is associated with sunburns.
- Ultraviolet C (UVC): This type of light has a wavelength of 100–279 nm.
UVA can penetrate windows and cloud cover and may cause tanning. There are associations between UVA and skin aging and UVB and skin burning.
UVA and UVB can both damage the DNA in skin cells. Prolonged exposure to either type of UV light may lead to skin cancer.
What are the symptoms of sunburn?
Sunburn in people of all skin tones will cause:
- a sensation of heat or warmth
- sensitivity to the touch
- peeling skin
- possible blistering
Symptoms usually start about 4 hours after sun exposure. They tend to worsen in 24–36 hours and usually resolve in 3–5 days.
Sunburn is often easier to detect in lighter skin, as it may appear red and inflamed. A person may find it harder to spot sunburn’s subtle redness or pinkness in People of Color.
As sunburn heals, the skin may peel away in the affected area. It is important to take care of the skin as it heals, though the sunburn itself should clear up on its own in a matter of days.
How crucial is sunscreen?
Currently, there are two types of sunscreen available: physical and chemical sunscreens.
Physical sunscreens, also called sunblocks, typically contain ingredients such as zinc oxide or titanium dioxide.
Chemical sunscreens contain chemicals that absorb UVB and UVA rays. In the United States, these typically include one of the following active ingredients:
- aminobenzoic acid
The Food and Drug Administration is currently reviewing the absorption of the active ingredients of chemical sunscreens into the body as well as the long-term effects of absorption.
Broad-spectrum sunscreens contain blockers that absorb both UVA and UVB rays. Each sunscreen will normally display a sun protection factor (SPF) on its container. A higher SPF number indicates better protection from sunburn.
Sunscreen is crucial because it reduces the amount of UV light penetrating the skin and reduces the risk of developing skin cancer.
According to the Centers for Disease Control and Prevention, a person should use a broad-spectrum sunscreen with an SPF of 15 or greater.
The Skin Cancer FoundationTrusted Source states that regular daily use of SPF 15 sunscreen may reduce the risk of squamous cell carcinoma, a type of skin cancer, by approximately 40%. Similarly, it may lower the risk of melanoma by 50%.
As UV light can penetrate clouds even during overcast weather, people should wear sunscreen even on cloudy days for effective protection.
There are many ways a person can protect their skin, reduce their exposure to UV rays, and prevent sunburn.
The American Cancer Society recommends:
- avoiding the outdoors when UV light is strongest, such as between 10 a.m. and 4 p.m.
- wearing clothing that covers the skin adequately
- using sunscreen
- wearing a hat with a brim of at least 2–3 inches
- wearing sunglasses that block UV rays
- considering wearing clothing with ultraviolet protection factor to block rays
The American Academy of Dermatology Association (AAD) recommends choosing a broad-spectrum sunscreen that is water resistant for 40–80 minutes and has an SPF of 30 or higher.
A person should also ensure that they apply enough sunscreen to exposed body areas. The AAD recommends approximately 1 ounce — about one shot glass full — to cover the full body.
A person should apply sunscreen about 15 minutes before going outside, as this is the approximate time it takes for the skin to absorb the sunscreen.
However, not all sunscreens are waterproof or sweatproof. No matter the SPF, a person should reapply sunscreen every 2 hours.
A person should ensure that they apply sunscreen to parts of the body that are easily missed, including:
- the top of the ears
- the back of the neck
- the part line of the scalp
- the top of the feet
- behind the knees
Melanin is a pigment found in skin, hair, and eyes. Melanocytes are cells that produce melanin. When they absorb UV rays, melanocytes increase melanin production in an attempt to protect skin from damage. People of Color have more melanin-producing cells.
Doctors consider tanning evidence of DNA injury. The more damaged the skin is, the more DNA will likely rewrite itself incorrectly and potentially result in a precancerous lesion or turn into cancer.
Melanin helps block out UV rays, but only up to a point. While the risk of experiencing sunburn is lower in a person with a darker skin tone, they should still apply sunscreen and limit their exposure to sunlight to reduce their risk of developing skin cancer.
Risk factors for sunburn
Some risk factors may increase the likelihood of someone experiencing sunburn.
Risk factors that may lead to sunburn include:
- having fair skin
- having lighter eyes, such as blue or green eyes
- having a lighter hair color, such as blond, red, or light brown
- being at high altitude
- taking medication that makes skin more sensitive to light, such as St. John’s wort
- taking medications such as tetracyclines, thiazide diuretics, sulfonamides, fluroquinolones
- taking nonsteroidal anti-inflammatory drugs
- using retinoids
- living in a tropical or subtropical climate
Sunburn occurs due to prolonged exposure to the sun’s UV rays. UVB and UVA are two types of UV light that cause changes to people’s skin. Doctors commonly associate UVB with sunburns.
UV light can penetrate clouds. For this reason, a person can still experience sunburn even during cloudy days or overcast weather. Symptoms of sunburn include hot or warm skin, itching, pain, occasional blistering, and peeling skin.
A person can reduce their risk of experiencing sunburn by using sunscreens with an SPF of 30 or higher, wearing appropriate clothing, limiting their time in the sun, and avoiding sun exposure when UV light is strongest — between 10 a.m. and 4 p.m.
Some people have a higher risk of experiencing sunburns, such as people with fair skin, people taking certain medication, and people who work or spend a prolonged amount of time outdoors.
A person should take protective measures, such as applying sunscreen frequently, regardless of skin tone, to reduce their risk of developing skin cancer.