What even is a UV index and the best numbers for basking in the sun, according to skin experts

• There is no safe or good UV index for tanning, since a tan indicates skin damage.
• If you do want to tan anyway, use sunscreen and try to go on days with the lowest possible number.

If you're hoping to get a tan (especially during the summer), you might want to know the best level of exposure to UV radiation to do so. However, it doesn't exist.

"There is no good UV index for tanning," says Dr. Cindy Wassef, assistant professor of dermatology at Rutgers Robert Wood Johnson Medical School. "There is no such thing as a safe tan."

If you still want to get a sun-kissed tan despite the risks — like premature aging and skin cancer — use sunscreen, reapply it frequently, and avoid the sun during its peak hours with help using the UV index.

Here's what you should know about the UV index and how to protect your skin from the sun.

How to use the UV index

"The UV index rates the strength of ultraviolet rays coming from the sun on a scale of 1 to 11, with higher numbers indicating stronger ultraviolet radiation," says Wassef.

Knowing the UV index forecast for the day can help guide your activity, clothing, and sunscreen choices, she adds.

Here is the breakdown of the UV index and the sun protection you need:

You can check the daily UV index for the day by downloading the UV Index Mobile App or entering either your ZIP code or city and state on the UV Index Search. You may also view a four-day UV Index Forecast to plan your activities for the next few days.

Aside from daily fluctuations, UV radiation changes intensity based on:

• Time of year: UV radiation peaks in spring and summer and is lowest in the winter.
• Location: UV is strongest at the equator and declines as you move toward the poles
• Elevation: As you get higher in elevation, UV radiation gets stronger

Is there a safe UV index for tanning?

When you're exposed to UV radiation, your body increases the production of melanin — the brown pigment that causes tanning — to protect the skin.

So by the time you actually see a tan, some damage to your skin has already occurred.

"As a dermatologist, I would say it is never okay to tan," says Dr. Susan Massick, a dermatologist at The Ohio State University Wexner Medical Center.

Massick adds that the safest UV index for being outdoors would be the lowest possible: <2. But even if the UV index is at the lowest level, you still must protect your skin with sunscreen.

In addition, those who resort to indoor tanning beds to avoid the sun's rays are actually most at risk of skin damage. The average sunbed emits UV radiation at an index of 12 to 13, which is incredibly strong.

Although data from 2018 shows that indoor tanning use in the US generally declined in recent years, about 7.8 million adults still use it today.

If you really want to get a tan, opt for "sunless" tanning creams containing dihydroxyacetone (DHA), a sugar that interacts with the proteins in your skin to produce a brownish pigment. It can give you a simulated tan without the risks associated with UV radiation.

Note: While DHA is FDA-approved for topical applications like cream or lotions, it is not approved for use in spray form — like at-home spray tans or misting from tanning booths — due to limited safety data. In fact, the use of DHA in aerosol spray form has been found to cause side effects like rashes, cough, dizziness, and fainting.

Risks of tanning

According to Massick and Wassef, tanning comes with a lot of risks, which include:

• Accelerated or premature aging
• Fine lines and wrinkles
• Brown spots
• Skin cancer

Excessive exposure to UV radiation — whether from sunlight or the use of indoor tanning — increases the risk for all types of skin cancer.

The best way to avoid the risks of tanning is to protect your skin from the sun. Here are some tips from Massick and Wassef:

• Apply a broad-spectrum, water-resistant sunscreen at least SPF 15 or higher about 15 to 20 minutes before heading outside.
• Re-apply sunscreen every 90 to 120 minutes when outdoors, especially if you're sweating or swimming.
• Always seek shade.
• Use hats, sunglasses, rash guards, and sun-protective clothing.
• Avoid the sun during its hottest hours, which are usually from 10 a.m. to 3 p.m.

"The more consistent you are with protecting your skin from the sun, the better off you'll be in preventing and avoiding the changes from cumulative sun exposure," Massick says.

Best sunscreens

For the best protection during all different times of the UV index, choosing the right sunscreen can be as important as applying it correctly. Here are some of the best sunscreens we've tested for all different skin types and tones:

• Best overall: Supergoop PLAY Everyday Lotion SPF 50, from $10 at Supergoop
• Best facial sunscreen: La Roche-Posay Anthelios Ultra-Light Mineral Sunscreen SPF 50, $34.99 at Amazon
• Best on a budget: Thinksport's SPF 50+ Sunscreen, $16.79 at Amazon
• Best spray-on: Supergoop Mineral Sunscreen Mist, $34 at Supergoop
• Best waterproof: Manda's SPF 50 Organic Sun Paste with Thanaka, $28 at Amazon

Insider's takeaway

Overexposure to UV radiation can cause premature aging and skin cancer. To guide your daily activities and level of sun protection, make sure to check the UV Index of the day before going out.

"When it comes to tanning, any degree of UV exposure can damage the health of your skin," Massick says. "There is no such thing as the 'healthy glow' or 'sun-kissed' look from a tan."