Translation:If we were in the desert, would it have rained?
Don't forget Dutch is a language and it has its own grammatical rules.. so forget about literal translations.
There are three ways to say "If we were in the desert, would it have rained?" in Dutch:
Als we in de woestijn waren, zou het hebben geregend?.
Als we in de woestijn zouden zijn, zou het hebben gereend?.
Als we in woestijn waren, had het geregend?.
The second one is less common, especially in spoken Dutch.
The first part is a supposition: "If we were in the desert..." The second part is a statement that, where the person is now (not in a desert), it is raining. The questioner is wondering would it have been raining like this IF they had been in a desert. Helpful?