有时，主句与从句的动作发生在不同的时间，主句从句谓语动词的虚拟语气形式因时间不同而不同，这种条件句叫做混合条件句。例如：
If you had asked him yesterday， you would know what to do now. 如果你昨天问过他，今天就知道做什么了。
(从句与过去事实相反，主句与现在事实相反。)
If it had rained last night(过去)， it would be very cold today (现在)。如果昨晚下过雨，今天就会很冷了。