Zürich has a singularly violent way to welcome summer: They roast a snowman until its head explodes.

At the spring holiday Sechseläuten, traditionally celebrated on the third Monday in April, residents build an effigy of winter in the shape of a giant snowman known as the Böögg, pack it with explosives, and set it afire.

“It is believed the shorter the combustion, the hotter and longer summer will be,” writes Bob Eckstein in The History of the Snowman. “When the head of the snowman explodes to smithereens, winter is considered officially over.”

The shortest time on record is 5 minutes 7 seconds, in 1974. The longest, just last year, is 43 minutes 34 seconds.