The race runs in late May in the Swiss Jura — early-season conditions that can vary dramatically. Recent race-day temperature ranges: 2026 high 25°C / low 13°C; 2025 high 19°C / low 7°C; 2024 high 14°C / low 6°C; 2023 high 20°C / low 6°C; 2022 high 14°C / low 1°C. Cold, wet editions are common: the 2025 race saw torrential overnight rain, mud, and fog on the ridgelines, with hypothermia affecting at least one elite finisher. A 2021 finisher account describes cold, foggy, rainy conditions at the Chasseron high point (1,606m) in what was nominally a June edition. Plan for cold overnight temperatures and wet conditions regardless of forecast, particularly on the Chasseron ridge and Les Aiguilles de Baulmes sections. Mandatory gear for the 114.8 km includes: ID card, eco cup, 1L minimum water capacity, headlamp, phone, survival blanket, whistle, waterproof jacket (10,000mm minimum), long-sleeve layer, pack, tape, and food reserve. A drop bag service is available at Noirvaux base camp (km 75). Aid stations: 11 official stations including hot pasta at the last three stations.