Yesterday in Ireland, on one of the warmest days of the year so far, Dubliners were treated to a natural wonder.

Spotted In Dublin!

— 98FM (@98FM) June 30, 2015

The skies above Dublin city filled with altocumulus lenticularis – clouds that bear a striking resemblance to flying saucers.

UFO Clouds are Awesome @LovinDublin @lecooldublin @DublinTown @DublinDiaries @dublin

— Cathy Burke (@CloudBurke) June 30, 2015

Lenticular clouds normally form perpendicular to the direction of the wind, in conditions where stable, moist air collides with mountains or large man-made structures.

RT @LiveNaasWeather The day #Dublin came under siege of UFOS! Altocumulus Lenticularis Clouds!

— Adrian Linares (@Adriansweather) June 30, 2015

Satellite imaging offered a birds-eye view of the clouds above Dublin yesterday.

High resolution visible satellite imagery of Dublin lenticular clouds from today.

— Tim Ballisty (@IrishEagle) June 30, 2015

The unique shapes the cloud formation takes on are thought to be one of the most common explanations for apparent UFO sightings.

Spectacular shot of todays #Lenticular #Clouds over Ballyfermot #Dublin 10 by Amanda Devlin. #Ireland

— Kildare Weather (@LiveNaasWeather) June 30, 2015

Have you ever seen lenticular clouds in person? Let us know in the comment section, below.