"It can rain today."
Translation:Puede llover hoy.
In this case lo shouldn't be used because "it" is not receiving any action. Remember that the conjugation for "it" is identical to the one for him/her/formal you.
edit: sorry, misunderstood. Correct me if I'm wrong, but se indicates an indirect object. The English sentence, "It may rain today," doesn't have an indirect object, either. It may rain today. [subject][helping verb][verb][time adverb] Puede llover hoy. [verb-subject conjugation][verb][time adverb]
You bring up a good point. "Poder" can be translated as "can" or "may," depending on context.
Does anyone know why "puede que llover hoy" is wrong? or when you can and can't use "que"?
You use "que" after any form of "tener" to mean "to." I am only conjecturing, but because the various declensions of "poder" can be used as a helping verb, I think that is the reason why "poder" does not take a "que" following it. Anyone know for sure?