While most Australians have had the "slip, slop, slap" message drilled into them from birth, researchers say the risk of skin damage under the sun's golden rays has been revealed in new detail - and must be taken more seriously.

Right now international health agencies only recommend sun protection when the UV index, which measures the maximum intensity of the sun's radiation each day, reaches three or higher.

But in a world-first study, researchers from the Australian National University and New Zealand's National Institute of Water and Atmosphere Research measured the total UV output throughout the full course of a day.

The results surprised even them, Robyn Lucas at the ANU said.

"It's an eye-opener, we've gone to the World Health Organisation a few times on this, and the importance of time spent in the sun, but we've never had the figures before," she said.

UV measurements were taken under the blue skies of Alexandra on New Zealand's South Island and in the slightly more turbulent climate of Melbourne.

The team found that, on average, cities like Melbourne only experienced two days a year where there wasn't enough UV to get sunburnt.

Further north, that number continued to shrink.

"I would suspect there would be no days in Canberra [and most of Australia] where you can't get sunburnt," Professor Lucas said.

"But I was surprised by the shortness of the time [we found] it took to actually get sunburnt."

In New Zealand, co-author of the study - and golf enthusiast - Dr Richard McKenzie was also taken aback by the findings. Even a few hours on the golf course on a winter's day could cause sunburn.

Professor Lucas, who has fair, European skin classified as "type two", admitted she would burn within 45 minutes to an hour outdoors on a low-UV day. And it would take even less time for her DNA to take on damage.

"Usually that kind of damage repairs itself before you burn, but the longer you're out, and the older you are, the less you can rely on that," she said.

For those particularly fair of skin in the "type one" category such as redheads - and this reporter - the window of safe time out in the sun shrunk even further.

"Someone pale like you would burn in say 30 minutes [in winter]," Professor Lucas said.

"Most people think if it's cold and they're covered, they're fine, but your face and hands are still exposed and those are the most common places for skin cancer."

The team said the data would likely come as a shock to health agencies, which have long favoured a simple message for guiding sun protection.

"Time complicates that, it's not just slip, slop, slap anymore but it's so important people understand.

"Even if the UV index is low, if you're outside for more than 10 or 15 minutes...you're at risk."