Abstract
The past 2021 was characterized by an outstanding amount of resonant weather disasters, one of which was an unusually strong heat wave in the European part of Russia. Why was the summer so hot and will such an abnormality be repeated regularly in the following years? To answer these questions, we first need to understand the typical characteristics of hot weather and the boundary between abnormal and normal conditions. The article discusses the criteria characterizing the high temperatures that have been observed on the territory of our country in recent decades. An illustration of their application is presented based on statistical data on summer temperatures in 2021 in three federal districts: Central, Northwestern, and Volga.