Our flight arrival in Milan is 6:00 pm. Our next destination is Varenna. Is it possible to clear customs , travel to train station and on to Varenna that evening and still be able to arrive in daylight? I've read that the first sight of Varenna/Lake Como is spectacular so would rather stay overnight in Milan and travel the next day if it will be dark the previous evening. Thanks for all the forthcoming tips.
It seems unlikely so you will probably want to stay overnight in Milan. You did give the date of your arrival or the airport (Malpensa or Linate?): on Aug 1 sunset is approx 8:05pm local time in Milan (about the same time for Varenna); however, if your arrival date is closer to Sept 1, sunset is approx 7:30pm. Either way, you would have to do the other things you mentioned and also wait for trains' scheduled departure times.
I'd been thinking about the same thing and ultimately decided to stay in Milan the first night. That way if the flight is delayed or whatever, it's no big deal to arrive later and miss out on Milan. It also takes me a day or two to get my "travel legs" anyway and adjust to the time change, so I thought I might as well spend the first crazy night in Milan and then head up to Varenna first thing the next morning. I found a budget hotel on Venere.com.