It depends on how likely the conditional event is, or how likely you would like to portray it as.
For a conditional clause expressing a possible future event, you have two choices: (i) put the inflected verb in present form, or (ii) put the inflected verb in preterite form. Use option (ii) if the contemplated event is unlikely or being posed as if contrary to fact. Use of the preterite does not in such a case imply past tense (and it obviously couldn't, since we're talking about a future event), it is instead called the "modal preterite", since it is used for a non-indicative mood.
The second clause should have its inflected verb in the same form as the conditional clause does.
If it rains tomorrow, I will go to the cinema. (It is likely to rain tomorrow)
If it rained tomorrow, I would go to the cinema. (There is no reason to believe that it will rain tomorrow, but it just might happen)