Seeing a whirlwind
In the lore of Ireland and the Scottish Highlands, seeing a whirlwind on a calm day meant the fairies were passing, and people greeted them or threw a shoe into the eddy. Today such whirls are called dust devils, born of hot ground.
What it may mean
What made the whirlwind uncanny was the stillness around it. On a calm summer day a small eddy goes past, whirling straws and dust, while not another breath of air is moving, as John Gregorson Campbell, minister of Tiree, put it. People supplied a traveler. In Ireland, W. B. Yeats wrote, it was the fairies passing, and country people took off their hats and said "God bless them." In the Highlands, people threw a left shoe, a bonnet or a knife into it to make the fairies drop whatever they were carrying off. One answer greets the thing, the other defends against it, and both come from people who lived with the same puzzle. A sudden swirl of leaves on a still afternoon can show you which of the two comes to you first.
Depending on how you saw it
Leaves spinning in the yard
A whirl of dry leaves can rise in one corner of a yard while the garden around it stays still. In Ireland, Yeats noted, straws and leaves whirling as the wind passed were the fairies' doing, and the answer was a blessing. Which brief, odd thing did you stop to watch this week?
A dust devil over a dry field
On hot, clear days dust devils often rise at the seam between two surfaces, and most fade within minutes. People stir things up at seams too, where work meets home or one group of friends meets another. Where do two of your worlds meet and kick up dust?
Throwing something into it
In the Scottish Highlands, people threw a left shoe at the eddy, or a bonnet with the words "This is yours, that's mine," so the fairies would drop what they had taken; in Ireland, clay was thrown. What would you want back badly enough to throw a shoe for?
Why it happens in nature
Small whirlwinds, or dust devils, form under clear skies and light winds where the ground heats strongly, often at the edge between surfaces such as asphalt and dirt. A pocket of hot air rises quickly, begins to spin and lifts dust and leaves. Most last only a few minutes and are smaller and weaker than a tornado.
What folk beliefs say
Ireland
When the wind made straws and leaves whirl as it passed, Irish country people took it for the fairies passing, raised their hats and said "God bless them."
Source: W. B. Yeats (ed.), Fairy and Folk Tales of the Irish Peasantry ("The Trooping Fairies") (1888), www.gutenberg.org. View the page
Scottish Highlands
Fairies leaving home in companies were said to travel in eddies of wind, called in Gaelic "the people's puff of wind"; throwing your left shoe, your bonnet, a knife or earth from a molehill at it made them drop the people or animals they were taking away.
Source: John Gregorson Campbell, Superstitions of the Highlands & Islands of Scotland (1900), pp. 24-25. View the page
Ireland
In Ireland, a whirlwind could be a devil dancing with a witch, or fairies rushing by to carry off a girl or a child, who could be saved by throwing clay at the passing wind.
Source: Cora Linn Daniels; C. M. Stevans (eds.), Encyclopaedia of Superstitions, Folklore, and the Occult Sciences of the World, vol. 2 (1903), vol. 2, p. 1037. View the page
To reflect on
When something you cannot explain passes close by, is your first move to greet it or to guard against it?