There are three days that it never rains in Moscow . These days are Victory Day, City Day and Russia Day.
However, the fact that it doesn’t rain during these days is not a matter of luck but a matter of scientific planning.
If rain is forecast for public holidays, the authorities make the rain clouds disappear before they get to Moscow, using a system that artificially stops rain from falling in a particular place.
A plane sprays chemicals close to the unwanted clouds, which makes it rain right there and then or makes the clouds disappear.