Crowded outdoor settings still put people at risk of contracting COVID-19, the WHO has warned.
Spokesperson Dr Margaret Harris says being "jam-packed together" outside is an issue, even with outdoors generally being safer than indoors.
It comes amid concerns around large crowds gathering in cities around Ireland during weekends.
Chief Medical Officer Dr Tony Holohan expressed surprise at the 'scale' of the outdoor gatherings in Dublin city centre last weekend, saying people were squeezed into a confined area in South William Street.
Pubs and restaurants will reopen for outdoor service tomorrow for the first time since Christmas, but in the meantime, there has been a weekend of unrest in Dublin city centre as gardaí work to disperse large crowds.
It comes as officials continue to encourage people to enjoy an 'outdoor summer' due to the increase risk of contracting COVID-19 indoors.
On Newstalk Breakfast, Dr Harris said the vast majority of COVID-19 super-spreader events happened indoors - but people still need to be careful when they're outside.
She said: "If you’re jam-packed together outdoors you still have a much higher risk of getting infected than if you’re outdoor enjoying the space but keeping your distance.
“Everyone needs to keep the three c’s in mind for the whole summer - avoid close contact for long period of time; avoid crowding; and avoid being in confined, closed spaces.
“When you’re outdoors you’ve eliminated one of those - the confined, closed spaces. But the crowding and being in physical close contact for a considerable period of time - I’m talking more than 15 minutes - still puts you at risk."
Meanwhile, concerns remain about the situation in Limerick amid a surge in coronavirus cases there.
The Health Minister has said the rate of COVID-19 in the county is simply too high, but that a local lockdown is not being considered.
Asked about the WHO's current stance on localised lockdown, Dr Harris said "targeted measures" are the best way to go.
She said: “It’s good to know exactly where the virus is… to really stamp it down.”
She suggested targeted measures can also be clearly explained to the local community - although acknowledged it can also cause difficulties if a local area feels they're being treated unfairly.