Key Points 

Extreme heat, heat wave 

• Brittany experienced an early heatwave in S22 (May 26–28), affecting the entire region. Record temperatures were observed.
  The seasonal monitoring system has been active since June 1 and will remain so until September 15. All departments in Brittany have been under a green heat wave alert since May 30, 2026. In S23, indicators returned to levels previously observed outside of periods of high heat.

Allergies

• Moderate activity.

ENT Conditions

• Moderate to low activity related to ENT conditions. In S23, among children under 5, ENT conditions accounted for 12% of emergency room visits and 48% of SOS Médecins consultations. The Virology Laboratory at Rennes University Hospital detected rhinoviruses/enteroviruses in 22% (12/55) of the samples tested.