Does the number of days with extremely high maximum air temperatures increase? The analysis below uses freely available data from the Czech Hydrometeorological institute. Meteorological stations used were those that have a complete data set between 1961 and 2022 (at least 11 months of data in each year). Number of days with maximum air temperature of a particular value was calculated for each of the 54 stations, in particular the number of days per year, when the daily maximum air temperature reached at least 30, 31, 32, 33, 34, 35, 36, 37 and 38 °C. Subsequently the number of days was summed up from all stations in each year. Given the fact that the same group of stations has been used in each year, the values are comparable and not affected for example by new stations in warm regions.
The graphs from all years assessed show that the number of days with extreme temperatures of 30 °C or more is increasing steadily. Temperatures above 35 °C were almost non-existent at the beginning of the period of assessment. In all cases, the number of days was significantly higher in the period 1991-2020 compared to 1961-1990 (sometimes by a factor of almost ten). The assessment was not carried out for days with a maximum temperature of 39 °C or more since such cases are very rare and the results could be significantly biased by just a few cases based on station selection and data availability.
In general, the highest temperature ever measured in the Czech Republic is 40.4 °C and was measured on August 20, 2012 in Dobřichovice. Until 2012, the absolute highest temperature measured was 40.2 °C, recorded on July 27, 1983 in Prague-Uhřiněves.