If it was more humid in the desert

[Freeguy]

If it was more humid in the desert of the southwest, the hot temperatures would be unbearable.


I know that we should say "If it were" instead of "if it was". But, would you please tell me that why we can't use was in this case?

 

[emsr2d2]

You will hear "If it was" as often as, if not more often than, "If it were" from many BrE speakers. The subjunctive voice is falling out of favour and out of use in many cases.

 

[MikeNewYork]

If it was more humid in the desert of the southwest, the hot temperatures would be unbearable.


I know that we should say "If it were" instead of "if it was". But, would you please tell me that why we can't use was in this case?

The first clause in your sentence is contrary to fact. That is why we use the subjunctive there. The subjunctive is still pretty common in AmE, but its use has probably decreased.