My brother finished the 42km ski marathon in Engadin in Switzerland on March 12 2006 [link] [Engadin link]. Conditions were harsh. The temperature was minus 20 degreed Celsius and he had a 60km/hour headwind.
Result: 5 hours – 26 minutes 51 seconds
Behind on winner: 2 hours 53 minutes 29 seconds
Avage speed: 7,7km/hours
I am more of the type who goes downhill and up the hill in a chairlift.