天气一热，我就想游泳。(tian qi yi re, wo jiu xiang you yong.)
In the construction “一 + Situation 1, 就 + Situation 2″, Situation 1 is the condition, whereas Situation 2 is what results directly from it.
“一” and “就” are both adverbs and should be placed after the subject and before the predicate. In the example above, “喝冰水” and “肚子疼” are both subject-predicate construction used as predicates.
In “他一进屋就睡觉了.”, “一……就……” is not a conditional compound sentence. It indicates one action takes place immediately after another, e.g: