Dear Dzmitry Pasrednik I think photoperiod sensitivity (specific eriod of darkness) of fruit trees for blooming could be the main reason. You can access an answer given in response to blooming of apple:

https://www.slader.com/discussion/question/explain-why-apple-trees-bloom-in-die-spring-but-not-in-die-summer-995c2688/

Best wishes, AKC

Dear Dzmitry Pasrednik, it is very nice observation. In general, fruit trees have a dormancy period in the winter and in the dormant season the buds inside/dormant stage wait for a small or reduced frost and a relatively less frost in the spring seasosn. So, as soon as the spring seasosn starts the buds of flowers start to bllom. You can read the following article (link attached). Thank you! https://www.canr.msu.edu/news/assessing_frost_and_freeze_damage_to_flowers_and_buds_of_fruit_trees

Arbind K. Choudhary and Girma Hailemichael Gebre

Thank you for your answers! As I understood, a longer vegetation period guarantees seeds maturation, and starting blooming during spring frosts gives more chances for it despite the fact that a plant could lose some flowers because of low temperatures.