Being a token girl on the forum, I'm just gonna say it, man up and ride dude!
For me, if it's sunny and dry (no black ice), I'm riding to work. my commute is about 20 minutes also, mostly freeway. I haven't had my knees get cold if I am wearing textile or leather pants. only fashion jeans
other than that, my fingers get really cold. and before I got grip warmers, I would lose my core heat, and it would take me hours to warm back up. Soo...
1) wear layers under your jacket, even under armor under your riding pants
2) heated grips - $45 bucks is to install, just need to know what + and - is on the battery and have some glue.
3) silk glove liners.
for a commute under 30 minutes, you are good to go. If you are under 5'9", consider laying a little or a lot on the tank, so you don't that blast of cold air on your chest.
4) mind over matter, suck it up baby!!