The right weather conditions for the Elfstedentocht skating race will only occur on average every 18 years, according to an article in the scientific magazine Climate Change due out on Friday.

Researchers Hans Vissers and Arthur Petersen of the planning agency for the environment based their calculations on average winter temperatures and the maximum ice thickness in the province of Friesland where the race is held.
The 18 years is an average, with a minimum gap between races of seven years and a maximum of 64 years, says the magazine.
The Elfstedentocht is a 200km long race through 11 towns in Friesland over natural ice. It was last held in 1997.
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