Questions & Answers about После дождя на улице грязно.
Because после always takes the genitive case. The basic dictionary form is дождь (rain), but after после it changes to дождя.
- дождь = nominative
- после дождя = after rain / after the rain
This is a very common pattern in Russian:
- после урока = after the lesson
- после работы = after work
- после обеда = after lunch
So после дождя is just the normal case form required by the preposition.
Because на улице is a fixed, very common Russian expression meaning outside or out on the street.
Here улица changes to the prepositional case because it follows на in a location meaning:
- улица = street
- на улице = on the street / outside
So grammatically, this is a location phrase: where is it dirty? → на улице.