Think of the UV Index as your personal sun-safety alert system: It measures how strong the sun’s ultraviolet rays are and how quickly they can damage your skin. This easy-to-understand guide explains everything you need to know about the UV Index, how the numbers are calculated, what exactly they mean, and who comes up with them.

The UV Index is a scale that measures the strength of the sun’s ultraviolet (UV) rays at a specific location and time. Ranging from 1 to 11 and above, the index helps people understand their risk of sunburn and skin damage. Lower numbers indicate minimal risk, while higher values signal increased danger and the need for protective measures such as sunscreen and shade.

National agencies such as the EPA and NOAA calculate the UV Index using standardized formulas that consider factors like time of day, cloud cover, altitude, latitude, and season. The scale was extended beyond 10 to accommodate higher UV levels observed in some regions. Monitoring the UV Index can help individuals reduce their risk of sunburn, skin cancer, and premature skin aging.

What is the UV Index and why should you care?

It's that time of year when the sun's rays are getting more and more intense for those of us in North America. So now's probably a good time for a quick review of the UV index. To start, the scale goes from 1 to 11 plus, and it tells you how strong the sun's ultraviolet or UV rays are at a specific place and time. So think of it like a sunburn meter. The higher the number, the faster your skin can burn. Down here at 1 to 2, the risk of sun damage is low. From 3 to 5, it's moderate, so start wearing sunscreen because you can get sunburns in that zone. Once you're at 6 to 7, that is a high UV risk. So you should really try to stay in the shade and limit your time outside. 8 or higher means your burn time can be super quick. And there's also a heightened risk of skin cancer and skin aging. So who decides these numbers? They're actually calculated by national agencies like the EPA and NOAA. They use a set of standardized formulas to shine some light on the answer, taking into account time of day, cloud cover, altitude, latitude, and season. And why is it out of 11? Well, it's actually out of infinity. It used to be out of 10, but some locations started hitting peaks above that threshold. So the current limit of 11 plus just includes anything that high.

Russia pummeled Kyiv with the largest drone attack of the war, injuring at least 23 people and damaging buildings across the capital only hours after U.S. President Donald Trump spoke with Russia's Vladimir Putin, officials said.

Kyiv

Ukraine Invasion

Russia hits Kyiv with largest drone attack after Trump-Putin call

U.S. President Donald Trump marked the passage of the new spending bill, which includes changes to food assistance, student loan programs, and clean energy credits. Robert Costa joins "CBS Mornings" to break down what's in the legislation.

Washington

Trump set to sign "big, beautiful bill"

More than 80 Palestinians were killed in Gaza on Thursday (July 3), according to health officials, as Israel intensified its strikes, hitting a school-turned-displacement facility. CNN’s Paula Hancocks looks at the damage and humanitarian toll.

Jerusalem

More than 80 people killed in Gaza in one day

Ukrainian President Volodymyr Zelenskyy said Kyiv will do "anything" to advance EU accession talks. Zelenskyy spoke alongside Danish Prime Minister Mette Frederiksen, President of the European Council António Costa and President of the European Commission Ursula von der Leyen.

Ukraine will do 'anything' to advance EU accession talks: Zelenskyy

President Donald Trump said Washington will start sending letters to countries on Friday specifying what tariff rates they will face on imports to the United States, a clear shift from earlier pledges to strike scores of individual deals.

Global Tariffs

Trump: Letters telling countries their tariff rate going out Friday

Indonesian rescuers on Thursday (July 3) temporarily halted a search for 30 people still missing after a ferry carrying 65 people sank near the island of Bali with the loss of six lives, the national search and rescue agency said.

Gilimanuk

Indonesia suspends search for 30 missing after ferry sinks near Bali

After marathon debate sessions in the Senate and House, President Donald Trump’s budget bill passed in the House. Republicans secured the biggest win of Trump’s presidency.

Trump’s landmark ‘big, beautiful bill’ narrowly passes U.S. House

Florida says the first group of migrant detainees have arrived at the new immigration detention center known as "Alligator Alcatraz." CBS News correspondent Shanelle Kaul has more.

Ochopee

First group of detainees arrive at "Alligator Alcatraz," Florida says

U.S. President Donald Trump said Thursday (July 3) that he spoke with Russian President Vladimir Putin and that he plans to hold a call with Ukrainian President Volodymyr Zelenskyy. CBS News White House reporter Willie James Inman has more.

Trump speaks with Putin, plans call with Zelenskyy

CNN’s Priscilla Alvarez reports on a lawsuit from lawyers for Kilmar Abrego Garcia alleging he suffered “torture and mistreatment” after he was wrongfully deported and held in El Salvador’s notorious mega prison.

Tecoluca

Kilmar Abrego Garcia claims he was tortured in El Salvadoran prison

The Kremlin welcomed the development, with spokesman Dmitry Peskov claiming it proves Western arsenals are being depleted and predicting that less aid will hasten the end of the conflict.

U.S. pauses military aid to Ukraine over depleted weapons stockpile

Two contractors employed by UG Solutions spoke to the AP on condition of anonymity as they were revealing their employers’ internal operations.

U.S. contractors say live ammo used at Gaza aid distribution site

Democratic leader Hakeem Jeffries spoke for hours on the House floor about potential impacts of President Trump's "big, beautiful bill" that Republicans are looking to pass before July 4. Following debate, the House is set for a final vote on the massive budget bill.

House debates Trump's 'big, beautiful bill' ahead of final vote

CBS News political contributor Caroline Polisi joins "CBS Mornings" to break down the jury's verdict in Sean "Diddy" Combs' federal trial and the judge's decision to deny bail for the music mogul ahead of his sentencing.

Manhattan

Sean "Diddy" Combs denied bail after split verdict

Liverpool soccer player Diogo Jota has died aged 28, just weeks after marrying his childhood sweetheart. The footballer passed away in a car crash in northern Spain.

Madrid

Liverpool soccer player dies in car crash 10 days after wedding

The Pentagon said that U.S. strikes 10 days ago had degraded Iran's nuclear program by up to two years, suggesting the U.S. military operation likely achieved its goals despite a far more cautious initial assessment that leaked to the public.

Tehran

Iran Strikes

Iran nuclear program degraded by up to two years: Pentagon

Days before his 90th birthday, the Dalai Lama announced the Gaden Phodrang Trust, a non-profit he founded, will have the sole authority to recognize his future reincarnation, but China insists it will choose the successor of the Tibetan spiritual leader.

Lhasa

China rejects Dalai Lama’s succession plan

The U.S. Congress inched towards approving President Donald Trump’s Big Beautiful Bill, despite attempts by Democrats to stop it. The bill is Trump’s signature legislation which includes massive spending increases on the military and immigration enforcement while slashing social programs.

Trump’s Big Beautiful Bill nears approval

Sean (Diddy) Combs was found guilty on prostitution-related charges, but was acquitted on more serious charges of racketeering and sex trafficking giving him a maximum sentence of 20 years. But the courtroom victory was subdued following a judge’s ruling to deny him bail.

New York

Diddy denied bail, avoids life in prison

President Trump says Israel has agreed to a 60-day ceasefire in Gaza, but it remains unclear if Hamas will accept the terms. CBS News senior foreign correspondent Debora Patta has more.

Trump says Israel has agreed to Gaza ceasefire conditions

Bryan Kohberger changed his plea to guilty Wednesday for the 2022 murders of four University of Idaho students. CBS News national correspondent Carter Evans has more on the case.

Boise

New details revealed as Kohberger pleads guilty for 2022 Idaho murders

The Wisconsin Supreme Court struck down a state abortion law that was adopted in 1849 in a 4-3 landmark decision. CBS News' Shanelle Kaul reports.

Madison

Wisconsin Supreme Court strikes down 176-year-old state abortion ban

Macron and Putin held regular discussions around the start of Russia's invasion of Ukraine, with Macron visiting Putin in Russia in February 2022, but dialogue eventually stalled.

Paris

Macron held 'substantial' phone call with Putin

President Trump toured “Alligator Alcatraz,” a migrant detention center he teamed up with Ron DeSantis to build in the Everglades.

Everglades

Protesters gather around ‘Alligator Alcatraz’ as President Trump visits

Jurors in Sean “Diddy” Combs’ federal criminal trial said they have reached a verdict on four of the five counts, but they cannot reach a verdict on Count 1, which is racketeering conspiracy. The judge has instructed the jury to keep deliberating. Deliberations will resume Wednesday (July 2).

Jury reaches partial verdict in Sean "Diddy" Combs case

The U.S. Senate passed the Republicans' reconciliation bill on Tuesday (July 1) after more than 24 hours of marathon voting on amendments. Vice President JD Vance cast the tie-breaking vote.

U.S. Senate passes Trump's "big, beautiful bill"

The new order does not rescind existing sanctions on ousted longtime President Bashar al-Assad, his top aides, officials and family members who are accused of having committed war crimes and human rights violations against Syrian civilians.

Trump signs executive order lifting U.S. sanctions on Syria

Former criminology graduate student Bryan Kohberger has agreed to plead guilty to killing four Idaho college students in 2022, a move that would spare him the death penalty under a deal with prosecutors, ABC News reported on Monday (June 30).

Moscow

Suspect in murders of four Idaho college students to plead guilty

Thailand's Constitutional Court on Tuesday suspended Prime Minister Paetongtarn Shinawatra from duty pending a case seeking her dismissal, adding to mounting pressure on a government fighting for survival on multiple fronts.

Bangkok

Thai court suspends PM from duty pending case seeking her dismissal

Israeli strikes killed at least 60 people across Gaza on June 30 in some of the heaviest attacks in weeks as Israeli officials were due in Washington for a new ceasefire push by U.S. President Donald Trump.