Over the past 10 years, Marathon du Mont-Blanc runners have faced temperatures ranging from 15\u00b0C (60\u00b0F) on cooler years to 25\u00b0C (77\u00b0F) in warmer editions. The median temperature of 21\u00b0C (70\u00b0F) puts this race in the challenging category for running conditions.
Wind speeds average 5 km/h during race hours, with peak gusts reaching 8 km/h in challenging years. Humidity sits around 61%, and there is a 30% chance of rain on race day.
These conditions translate to an estimated pace impact of +5.3% compared to ideal running conditions. For a 4-hour marathoner, that means roughly 13 minutes slower than a perfect-weather day.