During warm weather, if you can't wear shorts at work, you may want to bike in them and have "office" clothes at the office. andyprough already mentioned having a clean shirt, but I tend to change out as much as I can. I use my car days to tote the office clothes to and fro.

Also in warm weather, I take my coffee iced instead of hot. That (or some other cool drink) also helps with the cool down.