Heatwaves in Lebanon occur during summer when several consecutive days of abnormally high temperatures, often compounded by high coastal humidity, create sustained risks to human health, agriculture, water resources, energy demand, and wildfires. Their impacts are becoming increasingly severe, including heat-related illness and mortality, reduced labor capacity, crop and livestock losses, and growing pressure on electricity and water supplies. Advances in high-resolution forecasting now allow these events to be anticipated several days ahead, supporting early warning, public-health preparedness, and contingency planning.
Lebanon is experiencing an upward trend in the frequency, intensity, and duration of extreme heat, driven by climate change. Rising temperatures are causing heat thresholds to be exceeded more frequently and for longer periods, while humid conditions along the densely populated coast can push Heat Index values to dangerous levels. Vulnerability is further amplified by rapid urbanization, urban heat-island effects, population density, poverty, limited access to cooling, and unreliable electricity.
Lebanon’s climatic diversity presents an additional challenge: coastal, mountainous, and interior areas located only tens of kilometers apart can experience very different temperatures on the same day, making a single national heat threshold inappropriate. To address this, 35 years of ERA5-Land data (1991–2025) were used to establish locally relative thresholds for Lebanon’s microclimatic zones and subsequently for all 1,549 villages, based on the 95th percentiles of daily maximum temperature and maximum Heat Index. These village-level baselines are combined with Morphometric assessment downscale forecasts according to local elevation, allowing valley, coastal, and mountain communities to be assessed against conditions specific to their setting.
A five-day heat-stress hazard forecast is now operational, using ECMWF forecasts to classify each village into four hazard levels: No Heat Stress, Low Heat Stress, Medium Heat Stress and High Heat Stress, according to both the magnitude and persistence of threshold exceedance. Updated daily, the results are provided through an interactive web map and plain-language bulletins.
Lebanon is experiencing an upward trend in the frequency, intensity, and duration of extreme heat, driven by climate change. Rising temperatures are causing heat thresholds to be exceeded more frequently and for longer periods, while humid conditions along the densely populated coast can push Heat Index values to dangerous levels. Vulnerability is further amplified by rapid urbanization, urban heat-island effects, population density, poverty, limited access to cooling, and unreliable electricity.
Lebanon’s climatic diversity presents an additional challenge: coastal, mountainous, and interior areas located only tens of kilometers apart can experience very different temperatures on the same day, making a single national heat threshold inappropriate. To address this, 35 years of ERA5-Land data (1991–2025) were used to establish locally relative thresholds for Lebanon’s microclimatic zones and subsequently for all 1,549 villages, based on the 95th percentiles of daily maximum temperature and maximum Heat Index. These village-level baselines are combined with Morphometric assessment downscale forecasts according to local elevation, allowing valley, coastal, and mountain communities to be assessed against conditions specific to their setting.
A five-day heat-stress hazard forecast is now operational, using ECMWF forecasts to classify each village into four hazard levels: No Heat Stress, Low Heat Stress, Medium Heat Stress and High Heat Stress, according to both the magnitude and persistence of threshold exceedance. Updated daily, the results are provided through an interactive web map and plain-language bulletins.