The most recent sightings were reported lastSaturday (5 September), in Olhos de Agua (Albufeira), and around 35 kilometres away in the village of Ferragudo (Lagoa), both at about the same time.
An email sent to The Portugal News from holidaymaker Paul Lewis said “hundreds of flashing lights moving slowly across the sky at approximately 10h40pm” were sighted in the Olhos de Agua area and “witnessed by several hotel guests including myself.”
A resident in the village of Ferragudo also told The Portugal News that that same night “I was sitting outside on the balcony with my husband when we saw what looked like a shoal of shimmering stars moving slowly through the sky. It was a bit like a cloud of tiny lights.
“We watched it move for about 15 minutes but it was too far away for our phone cameras to pick up. We tried to film it; it was 10.38pm”
Readers commenting on The Portugal News’ website in recent weeks have also given accounts of similar sightings.
A group of several Britons in Cascais witnessed something similar last month, on 19 August, and said: “This was not fireflies or any reflected lighting; [it was] a group of pure white twinkling stars in the stratosphere, they stayed over us and then slowly moved out to sea. It was really incredible.”
André Magalhães from Oporto said: “I saw this two times, on Sunday, 9 August”, while another observer in the Algarve said: “We saw the same on Friday, 15 May 2015 in Tavira.
“The lights travelled like a swarm of birds, and the lights were blinking continuously - on/off. Definitely a swarm of animals of some sort.”
A spate of similar sightings were reported in 2013 in Cascais, when a number of eyewitness accounts described unusual light phenomena in the night sky in and around the area throughout the months of June and July.
At the time, in response to questions posed by The Portugal News, a spokesperson for the Sintra-Cascais Natural Park (PNSC) said the lights “could well be a type of firefly”, which comes out when the weather warms up.
However, this suggestion is rebuffed by those who witnessed the more recent phenomena, as “it seemed too high up to be a flying insect”, the Ferragudo resident
recalled.
Another possible explanation for the phenomenon comes from the website UFO Portugal, which has also received numerous sightings of “agglomerates of lights that flash intermittently” in recent months, from north to south of Portugal.
UFO Portugal believes the sightings are LED balloons.
“It is quite natural that many people are unaware of the phenomenon, however the most plausible explanation for these sightings is the release of LED balloons.
“The LED [lights] are embedded inside the balloons that are in turn released into the atmosphere creating a light show in the night sky.
“At a certain altitude the balloons are no longer perceptible and all that is visible are the LED lights within them”, the website explained.
This theory is corroborated by the Astronomical Observatory in Lisbon, which this week told The Portugal News: “Recently the releasing of balloons with LEDs has become fashionable almost nationwide at birthday parties, weddings, etc…
“And when people observe this phenomenon at night, at a distance from the site [of release], it can be confused with stars.”