In 2015, large parts of Europe were characterized by extraordinary high summer temperatures, accompanied by very dry conditions, particularly in central‐eastern Europe. Several major heat episodes occurred from the end of June until mid‐September. We provide an ad‐hoc evaluation of the observed climatological extremes in a secular context, by using a set of long station time series in daily resolution. Our data set comprises 42 temperature and 43 precipitation records, predominantly starting already in the 19th century. To investigate local record values, the individual full record length is analysed for each station, while regionally averaged analyses are presented for the core study period of 1901–2015. The study area covers Europe's central latitudes (44° to 52°N), extending from England in the west up to the central Ukraine in the east.During summer 2015, various indices representing extremely high maximum and minimum temperatures (strongly) exceeded previous record high values, mainly in an area extending from eastern Germany to western Ukraine. Additionally, severely to extremely dry conditions with unusually frequent dry days were prevailing particularly in the (central‐) eastern part of the study area. Drought indices combining temperature and precipitation revealed drought conditions comparable or even worse than those of former extreme summers like 2003.

Spatial and temporal trend variability in extreme precipitation indices was studied for the meteorological seasons from 1951 to 2006. Eight indices were used, describing their frequency (90pNoD, 95pNoD), totals (1dayT, 5dayT, 90pT, 95pT) and intensity (90pInt, 95pInt). The following key challenges were addressed: (1) temporal variability in the relative number of stations with significant 30‐year trends, (2) temporal stability and (3) average magnitude of the calculated 30‐year trends. Temporal changes in the spatial extent of statistically significant extreme precipitation trends proceeded differently in each season. The trend direction, indicated by trend stability analysis, was consistent with that of averaged 30‐year trend magnitudes at most stations. A distinct spatial differentiation emerged in the prevailing trend directions between the eastern and the western part of the study area. In all seasons, increasing trends in extreme precipitation dominated in central‐eastern Germany, whereas opposite trends prevailed in southern Poland. This pattern was particularly prominent in winter. Similarities in the temporal variability of the percentage of significant trends between the eastern and the western sub‐regions emerged in autumn only. Summer was characterized by the most pronounced temporal changes in the percentage of significant negative trends. Summer also showed the most stable extreme precipitation trends of all seasons and a higher trend magnitude than the transitional seasons. Spatial patterns of trend directions in spring, showing the most complex pattern of all seasons, vary depending on the index, particularly with respect to trend stability. Copyright © 2010 Royal Meteorological Society

The year 2018 was affected by very long‐lasting, stable summer conditions in vast parts of Europe, in many regions already starting in April and lasting until October. We investigate the thermal characteristics of this year in a secular time perspective, using a spatially well‐distributed dataset of 67 European stations (west of ca. 30° E) with daily long‐term air temperature observations. Our dataset comprises many of the longest and most reliable (homogenous) temperature measurements available in Europe, mainly starting already in the 19^th or rarely even 18^th century. Individual time series length is considered to analyse the summer 2018 temperatures into a more than two century time perspective, while European time series are presented for the period 1855–2018 and records of five European regions are considered from 1881 onwards. The extreme long duration of the 2018 summer most clearly manifested itself in pronounced new continental maxima of summer half year (April – September) temperature averages and the number of days with maximum temperatures ≥20 and ≥25°C. Furthermore, those indices reached new local maxima at about half of our investigated stations. Records of other temperature indices, rather representing intense heat conditions, were particularly broken in the extended Baltic Sea region, supported by distinct and long‐lasting anticyclonic conditions in this area. However, the extreme summer of 2003 still dominates the ranking of most of these indices on the continental level, even though it is now generally closely followed by summer 2018. We show that long‐term variations of teleconnection indices and the Atlantic Multidecadal Oscillation, as well as seasonal and anthropogenic effects, supported both the recent hot summers and the extreme summer of 2018.

During the last 20 years some very hot and dry summers affected Europe, resulting in regionally record‐breaking high temperature or low precipitation values. Long‐term changes of such extremely hot and dry summers are of great relevance for our society, as they are connected with manifold negative impacts on human society, natural ecosystems, and diverse economic sectors. Long‐term variations in drought and five record drought summer half years are studied based on 63 stations across Europe with high‐quality precipitation and temperature time series spanning the period 1901–2018. Eight drought indices are deployed to analyse drought intensity, frequency, and duration; four of them purely precipitation‐based and four integrating potential evapotranspiration in the computation. Additionally, three heavy precipitation indices and simultaneous increases in drought and heavy precipitation are studied. The five driest summer half years over Europe are identified (1947, 2018, 2003, 1921, and 1911). They are analysed by aggregating eight drought indices into the aggregated drought evaluation index (ADE) for five subregions. The ADE shows increasing summer drought conditions over most of Europe, except for some stations in northern Europe. The increase in drought conditions during the warm part of the year is particularly pronounced for indices integrating evapotranspiration in their definition. At the same time, the intensity of heavy precipitation events shows a positive trend, as well as an increased contribution to total precipitation. Several stations in central Europe show simultaneously increasing drought conditions and increasing heavy precipitation events. This increases the risks connected with precipitation extremes.