Can you burn faster on a cloudy day?

Briefly, yes. Broken cloud can reflect extra UV onto you (cloud enhancement), pushing the level above clear-sky readings for short spells. Mostly, though, cloudy-day burns come from staying out longer without protection, not from stronger UV.

Do I need sunscreen if it's raining?

Heavy, dark rain cloud does block most UV, a genuinely bleak day usually sits below the protection threshold in southern Australia. But showery days with bright breaks behave like broken-cloud days. Go by the UV index: 3 or above means protect.

Can you tan through clouds?

Yes, skin responds to the UV that gets through, which is most of it under light cloud. If there's enough UV to tan, there's enough to damage skin, so the same protection rules apply.

Can you get sunburnt on a cloudy day? Yes, here's why

Yes, and it happens constantly. Up to 80% of UV radiation passes through light cloud cover, and some of the worst sunburns in Australia are collected under grey skies, because nobody reached for the sunscreen. Cloud changes how the day feels; it changes the UV far less.

What cloud actually does to UV

Clouds are good at blocking infrared, the warmth you feel, which is exactly why overcast days feel so deceptively safe. UV is a different story. Thin or high cloud barely attenuates it; the World Health Organization's guidance puts transmission through light cloud at up to 80%, and SunSmart repeats the figure for Australian conditions. Only thick, dark, rain-bearing cloud cuts UV substantially.

Broken cloud has a stranger trick: for short periods, scattered clouds can boost UV above the clear-sky level, as sunlight reflects off cloud edges and reaches you both directly and indirectly. Researchers call it cloud enhancement, a partly cloudy day can briefly deliver more UV than a cloudless one.

Why cloudy-day burns are so common

The warning system is off. No glare, no heat on your skin, so the sunscreen and hat stay in the bag.
People stay out longer. A cool, overcast 22°C is perfect for a long walk, a full day of sport, hours of gardening, more time for a slightly reduced dose to accumulate.
The UV was high to begin with. In an Australian summer, 80% of UV 12 is still nearly UV 10, deep in the 'very high' band. Cloud takes the edge off an extreme reading and leaves you with a merely dangerous one.

The rule that never fails

Judge the day by the UV index, never the sky. The forecast UV already accounts for expected cloud; live readings account for actual conditions. If it's 3 or above, cloudy, cool, windy, whatever, protection is on. Check today's UV for your city or get a burn-time estimate for your skin in about a minute.

Frequently asked questions

Can you burn faster on a cloudy day?: Briefly, yes. Broken cloud can reflect extra UV onto you (cloud enhancement), pushing the level above clear-sky readings for short spells. Mostly, though, cloudy-day burns come from staying out longer without protection, not from stronger UV.
Do I need sunscreen if it's raining?: Heavy, dark rain cloud does block most UV, a genuinely bleak day usually sits below the protection threshold in southern Australia. But showery days with bright breaks behave like broken-cloud days. Go by the UV index: 3 or above means protect.
Can you tan through clouds?: Yes, skin responds to the UV that gets through, which is most of it under light cloud. If there's enough UV to tan, there's enough to damage skin, so the same protection rules apply.

Keep reading

The sky lies. The UV index doesn't.

Check the live UV where you're standing and what it means for your skin type.

Check my burn time