Temperature swings

Today started near 40 degrees and had climbed to the 70s by the time I rode home. Dealing with this requires a couple layers. I wore my winter suit today, and removed my sweatshirt and liner for the ride home. I also opened up a lot of vents on the jacket. My torso was fairly comfortable, but the pants aren't vented and my legs were not nearly so comfortable. I need to find a better solution for my legs for these sorts of temperature swings. I've discovered that the comfort level of the bike's seat goes down a lot when I can't cool down my legs on a hot day. Perhaps the wrong seat is the problem.