A flying ant lands on court during last year's Wimbledon Championships.
London CNN  — 

On one day every year, as per tradition, Britain is invaded by swarms of flying ants – and this year, the insects arrived in such vast numbers they were seen from space.

The insects swept into the south of England on Tuesday, in an invasion that – at first glance – seems to indicate we are living in the early stages of a disaster movie.

So huge were the storms that weather radar mistook them for rain – a far more common phenomena on the British Isles.

BBC Weather presenter and meteorologist Simon King noticed the error, writing on Twitter alongside a video of the radar readings: “Flying ants!!! Swarms of them flying into the sky in S Eng are being picked up as rain on the radar image this morning…!”

But while the attack may seem unusual, it merely signaled the annual arrival of what has come to be known as Flying Ant Day.

Mobs of the insects descend on locations around Britain on one day every summer. The creatures sweep in and take up residence on streets, green land and in the skies before disappearing hours later.

The phenomena occurs because male and queen ants leave their colonies to mate when conditions are just right. And while flying ants are spotted on several days throughout the year, the vast majority pick the exact same moment to head out from their nests.

It led to disruption for Britons intending to make the most of the outdoors on Tuesday and Wednesday, when the country was bathing in sunshine and warm temperatures.

But the famous British stiff upper lip came in handy and people across the nation kept calm and carried on – aside from some outbursts of disgust on social media.

The event has been known to cause chaos at outdoor events; in recent years, players at the Wimbledon tennis championships struggled to maintain their focus as swarms descended onto Centre Court.

According to the Royal Society of Biology (RSB), the vast majority of the creatures all come from the same variety of flying ants – the black pavement ant Lasius niger.

But while the annual attack may be inconvenient, it could be valuable for Britain’s ecology.

The insects’ activity “allows for more oxygen and water to reach the roots of plants and they can even improve soil fertility and help control pests,” according to the RSB.