Extreme high temperatures and heatwave events across Europe in 2023

With global mean temperatures reaching record highs in 2023, many regions experienced successive heatwaves, causing negative impacts on human health, social economy, and ecosystems. Europe is among the continents that experienced a series of extreme heatwaves over large areas in the year. However, there is a lack of quantitative analysis of spatial and temporal features of such record high heatwaves. Here, we investigated the spatial patterns and seasonal evolution of heatwaves over Europe in 2023. Overall, Europe was unusually warm with prolonged seasons and expanded spatial extent of heatwaves in 2023 compared to the baseline period (1991-2020). The earliest heatwave occurred in the Iberian Peninsula in late April, with the heatwave intensity up to 30 degrees C. Then, heatwaves were observed in the British Isles and Scandinavia in mid-June successively, with duration above 10 days and the highest intensity in some areas since 1991. Extreme heatwaves extended through the autumn primarily in the Mediterranean areas and western Europe, with some areas experiencing maximum temperature up to 32 degrees C and duration exceeding 12 days. The heatwave number, duration, frequency, and intensity in areas affected by extreme heatwaves in all seasons were much higher than the average in the baseline period. Especially in the autumn, the frequency and seasonal cumulative heat anomalies were up to 25 days and 65 degrees C in some areas, respectively. These findings unveil the characteristics of heatwaves in Europe across seasons in 2023 and sound the alarm for developing adaptation measures to extreme heat events.