Vol. 69, No. 4 * Pages 214–272 * October 2024.

In mid-September 2024, Cyclone Boris caused heavy rainfall in the upper Danube catchment, causing extreme river flooding on the Danube and its tributaries. During almost a week, precipitation amount exceeded 200 mm in many areas with amount of over 300 mm recorded in large areas of Lower and Upper Austria. In Hungary, Western Transdanubia received the most precipitation exceeding 100 mm in some places. On the backside of Cyclone Boris, wind gusts exceeding 100 km/h caused storm damage in the area of Lake Balaton. Temperatures dropped sharply from 30 degrees Celsius to around 10 degrees Celsius. The sudden cooling during the bird migration period caused mass bird mortality, especially among swallows.

A clear sign of climate change in our region is the increasing frequency of weather and climate extremes, such as summer heatwaves, which may become longer and more intense in the future. In this paper the detection of heatwave periods and the analysis of different characteristics are carried out for two major cities of Hungary (Budapest, Szeged) based on station data series. In addition, based on data from the regional climate models available in the CORDEX programme, expected changes in the annual number of heatwave days over Hungary and mean characteristics of heatwaves are investigated until the end of the 21st century (reference period: 1976–2005). In our study, a more complex set of criteria, optimised for the climatic conditions of Hungary, is used to define heatwaves. According to our results, the average duration of heatwave periods could become 3–9 days longer by the end of the 21st century.

The record warm July of 2024 in Hungary gives us an idea of what the future holds. The observation series we analysed consist of homogenised and interpolated countrywide averages for July based on the HungaroMet national climate database. To estimate the likely changes, we used a set of regional climate model simulations available produced at HungaroMet for mapping the impacts of climate change in Hungary. According to the climate model simulations, cooler July temperatures (with means below 20 °C) may occur in the future too, but also July temperatures much hotter than in 2024 will be possible. We examined two 30-year periods in the near future and far future (2051–2080 and 2061–2090). A quarter of July temperatures are projected to be higher than in 2024 by mid-century, and one-third of July temperatures at the end of the century. It means that July mean temperatures similar to this year's could become common in the period of 2071–2100. The observed tendency suggests a temperature increase closer to the upper bound of the climate model simulations.

Dependence of the heart rate and skin surface evaporation (E ) on the thermal load of selected summer weather situations is analyzed. The heart rate is measured with a smart watch, the skin surface evaporation is simulated by measuring the latent heat flux density (E i) of the sweated water and estimating the potential evaporation of the atmosphere (Ep). During the measurements, the clothing was unchanged: the minimum summer clothing determined by behavioral standards. There were 3 activity types: lying position, walking and running. These movement states were characterized by the average speed of the movement. Our most important results: a) the heart rate only changed depending on the movement state, b) the skin surface evaporation varied between 40-330 Wm -2 and c) the model cannot be applied to estimate the evaporative resistance of the skin surface in all those cases when Ei > Ep. The frequency of individual human biometeorological analyzes can increase significantly with the spread and use of smart devices.

In January 2024, in many places of the Northern Hemisphere occurred extreme weather. More extremely strong winter storm swept through North America, then bomb cyclones formed over the Atlantic Ocean and reached Europe. Extreme weather cases – which were part of interrelated meteorological events – caused many problems in both continents. The arctic outbreak in America caused strengthening of the jet stream and the jet stream triggered rapidly deepening cyclones. The warm and moist air mass from low latitudes also contributed to the further developing of Atlantic cyclones.

Lajos Lóczy was a renowned geologist and an expert of the regions of China Proper and the Balaton highlands (Balatonfelvidék). He studied the evaporation of water in the Kereked Bay of Balaton in the summers of 1897 and 98. He observed a sediment on the bottom of the bailer. When measured, it amounted to 55.27 g/m 2 /month. “…I imagine the importance of these examinations is becoming aware to the possibility of measuring the subaeric fallout.” He was the first to do so according to our current knowledge. Sediment from fallout was being measured from 1962-64 and in 1976 at similar coastal locations. Average sedimentation was 5.6-6.4 g/m2 /month. The difference by order of magnitude is most likely due to environmental factors and sampling differences. Lajos Lóczy recommended the monitoring of atmospheric fallout nationwide. His idea was realized in 1976.