The purpose of this research is to analyze the characteristics of heatwaves during the warm period of the year as a manifestation of climatic changes in Ukraine. It was also our goal to establish how reliable Heat and Cold Wave Index (HCWI) from European Drought Observatory (EDO) is as a tool for heatwaves analysis. To extract the frequency and duration of heatwaves the percentile thresholds of 90th were used. The data from Ukraine’ weather stations since 1980 to 2021 were under analysis. There are 83 heatwave (HW) recorded in Ukraine. At the same time, for the first half-period (1980-2000) 29 events of heatwaves were recorded, and for second half-period (2001-2021) − already 54 events. The duration of heatwaves increased during the study period. If for 1980-2000 the average duration of the heatwaves was 3.8 days, then for 2001-2021 the average duration increased to 4.3 days. The average maximum length of heatwaves increased more significantly − from 7.4 to 11.5 days in the second half-period. The intensity of heatwaves was evaluated by temperature extreme. The average maximal temperature (1980-2021) during the heatwaves over Ukraine is 32.2ºC. The hottest HW event for the study period had maximum daily temperature of 41.4ºC (2010). For the first time, HCWI was used to determine the frequency, duration and intensity of heatwaves in Ukraine. HCWI can also be applied to study climate changes, determine the period of droughts, the adaptation of the population to heat stress and the healthcare system to its consequences.