MeteoLux is preparing an overhaul of its heat alert system.
In a press release published on Thursday, the Luxembourg meteorological service announced that a new system will be implemented from summer 2026 to better take into account the perceived temperature and the effects of heat waves on health.
Until now, alerts were based primarily on the maximum recorded temperature and that of the previous day. This approach is now considered insufficient to reflect the reality experienced by the public during particularly heavy and humid periods of time.
Meteolux's new system will use the UTCI, or "Universal Thermal Climate Index," an indicator developed by international experts and used by the European Copernicus programme. This index takes into account several factors simultaneously: air temperature, humidity, wind, and UV radiation.
In practical terms, future alerts will aim to reflect the heat as it is actually felt by the human body, and not just the value displayed on the thermometer.
In addition, the duration of heat waves will now be factored into calculations for the alert level. MeteoLux highlighted that health risks increase significantly when high temperatures persist for several days, particularly when nights remain warm and prevent the body from recovering.
Three alert levels will be maintained: yellow, orange, and red. However, the red level will only be triggered in the event of extreme heat stress for at least three consecutive days, with very high perceived temperatures also occurring at night.
According to MeteoLux, this choice is based on current scientific knowledge regarding the health risks associated with prolonged heat waves.
Alerts can be issued up to 48 hours in advance to allow the public and authorities to better prepare. The meteorological service said it wants to offer "more reliable, understandable and useful" alerts as heat waves are expected to become more frequent.
