Heat guidance

For riders

WBGT (Wet Bulb Globe Temperature) combines air temperature, humidity, wind, and solar radiation into a single heat-stress number — it's a better measure of real physiological load than air temperature alone, because it captures how much the body can actually cool itself by sweating in the given conditions.

Elite exertion changes the risk calculus: sustained high-power output generates substantial internal heat regardless of ambient conditions, and elite cyclists have recorded core temperatures of 39–41.5°C during hot races. Airflow at speed and downhill recovery sections provide some cooling that a stationary WBGT reading doesn't capture — which is part of why the UCI's 28°C threshold sits above general occupational safety limits (ISO 7243 uses 25°C for high-exertion work).

The UCI High Temperature Protocol maps WBGT to five risk tiers, each with escalating measures:

WBGT	Tier	Action
< 15°C	Very low-risk	No specific measures.
15–17.9°C	Low-risk	Warm-up in the shade with fans.
18–22.9°C	Moderate low-risk	Ice vests, wet towels, individualized hydration plans, ice socks.
23–27.9°C	Moderate high-risk	Shaded start areas, more drink/ice motorbikes, adapted hydration rules.
≥ 28°C	High-risk	Modified start/finish times or route, or cancellation.

Basic prevention — pre-cooling, staying ahead of fluid losses rather than drinking to thirst, and heat acclimatisation over 1-2 weeks before a hot event — is drawn from established sports-medicine guidance and the UCI protocol itself, not a substitute for advice from a team doctor or physiologist.

For roadside fans

France uses a four-level heat vigilance system (Météo-France, in coordination with Santé publique France for the highest level):

Vert (green) — normal conditions, no particular vigilance needed.
Jaune (yellow) — a brief heat peak (1-2 days). Mainly a risk for people already in fragile health or working outdoors; stay aware but no need to change plans.
Orange — an official canicule (heatwave): intense heat for at least 3 consecutive days and nights, risking the whole population, not just vulnerable groups. Hydrate constantly, avoid roughly noon–4pm direct sun, and seek cool/air-conditioned spaces for a few hours a day.
Rouge (red) — an exceptional, extreme heatwave, dangerous for everyone including healthy people. Expect possible event disruptions; prioritize shade and indoor cooling over watching the race live during peak hours.

What the protocol means

The UCI's Extreme Weather Protocol (2015, covering cold, wind, snow, and visibility as well as heat) was extended with a dedicated High Temperature Protocol in 2023–24, using the WBGT tiers above. At the red tier, the UCI can modify a stage's start or finish time, shorten or reroute it, or cancel it outright.

Separately, French media coverage of the 2026 Tour referred to stages being raced under a "Code Red" heat alert. This isn't a distinct legal category — it's journalistic shorthand for Météo-France's vigilance rouge heatwave level combined with a French Interior Ministry circular authorizing regional préfets to cancel a Tour stage, in consultation with the race organizer, when conditions no longer allow for the safety of spectators, staff, and emergency response. That power sits with local government, not the UCI, and is separate from (though often triggered alongside) the UCI's own WBGT-based protocol.