In Summer 2003, a severe heat wave struck parts of Europe beginning in June that continued through July and August. The extreme weather was caused by a high pressure area firmly anchored above Western Europe that persisted for weeks. In particular, the number of warm nights was much higher than the 1961-1990 normal in a large part of Central and Western Europe (red circles dominate the ECA&D anomaly map below). In the area with large red circles, there were more than 40 extra warm nights compared to a normal summer season.
ECA&D anomaly map of the number of warm nights during the summer months, June, July and August, of 2003 compared to the normal period 1961-1990. Please click on the map for its most recent version.
This anomaly corresponded with the summer month (June, July and August) mean temperatures that were more than 3°C higher than the 1961-1990 normal as shown in the ECA&D anomaly map below.
ECA&D anomaly map of mean temperature anomalies during the summer months, June, July and August, of 2003 compared to the normal period 1961-1990. Please click on the map for its most recent version.
In many locations across the continent, the long-term 90th percentile of maximum temperature, often referred to as "hot days", was exceeded for up to 60 days during Summer 2003.
ECA&D anomaly map of the number of days in June, July and August 2003 with maximum temperature over the 90th percentile compared to the normal period 1961-1990. Please click on the map for its most recent version.
August was the hottest month and saw temperatures in the UK, Germany, the Netherlands, Switzerland and Spain break all-time records. In France and Italy, the temperature soared to around 40°C for weeks. E-OBS data for the anomaly in the maximum temperature during August, shown below, reveals that there were warmer than normal temperatures everywhere with the most extreme warming occurring in Central Europe.
E-OBS maximum temperature anomalies for August 2003 compared to the normal period 1961-1990.
The number of days in summer that are part of warm spells has increased significantly over almost all of Europe since 1961 (with the exception of some stations in Northern Scandinavia). See the ECA&D trend map below.
ECA&D trend map of the summer warm spell duration index (WSDI) over the period 1961-2010. Please click on the map for its most recent version.
This extended period of extreme temperatures had enormous adverse effects on people and the environment. Over 30,000 people died, mostly the vulnerable elderly, and nearly 650,000 hectares of land burned in more than 25,000 fires across Europe. The heat also led to a glacier volume loss on the order of 5 to 10% in the Alps.