Dear (имя друга),
Winters in (свой город) are cold and windy with a lot of snow.But summers are rather hot and dry.That is why I'd like you to visit the capital of Russia in summer.Besides,my summer holidays are really long.Ihave so much free time that we could do a lot of things.We could go on excursions,travel or relax in the country.There we could play volleyball,go cycling,swin,sunbathe and spend a lot of time outdoors.
I wish you visited me in summer.
Best wishes,(твое имя).