I sweat the most in the winter, and in the summer commutes home.

In the winter, it's because I don't have a wind-proof shell that breathes worth a damn. Doesn't matter what I wear under it, or if it's 40 or 30 or 20 out.

In the summer, it's the 10 miles in 102 degree temps and sunshine that do it.

I don't care though, my commute IS my workout, and I have showers at both ends of the ride.