I am growing F1 Cherry tomato (Sweet Aperitif,Sweet Million, Sun Gold), they set flowers, and some flowers drop and start to get fruits, the weather is clear and between 23C to 30C most days, but yesterday and today the weather was 40C all the morning, I know that the high temp more than 40C degree is reducing fruit set , but is this true for my case which is just 2 days of high temp?
That is quite hot, but in my experience they can handle a few hot days (with adequate water).
Proper Nighttime temp is critical for fruit set - if nights are too hot they just won't set fruit and flowers will drop.
This article has good details
The article specifies that
Tomato flowers must be pollinated within approximately 50 hours or they will abort and drop off.
And also that
If nighttime temperatures fall below 55°F or rise above 70°F, or if daytime temperatures rise above 85°F, the pollen becomes tacky and nonviable, preventing pollination from occurring and causing the blossom to dry and drop
So 2 days at 40c is pretty close to that 50 hours, so very possible.
They also note that very high temps can directly cause blossoms to drop
Temperatures over 104°F for only 4 hours can cause the flowers to abort.
So overall I would say yes the two days at 40c are likely responsible, but that depending on the strain and the growing environment it's possible for tomatoes to withstand some pretty high daytime temps provided nighttime temps drop to an appropriate level.