I sometimes ride in my work pants which are drip dry poly blend and a casual dress shirt (if there is such a thing). However there is a risk of getting chain grease on your pant leg so I usually only do it in black pants, and of course I use a velcro cuff strap. The shirt is less of a worry. I always have one backup set of clothes at the office, but I bring clothes most days anyway just in case I brought the spare office clothes home and forgot that I did!

I don't usually have to shower at work until it gets up to high 20s (close to 80 F) and humid. But that's partly because my morning ride is mostly downhill and I can coast a lot on hot days.