Congrats, Dana, on the new job!
I just started one of my own a few weeks ago - it feels like the first 'real' job I've had in many years -- one I actually had to apply for, interview for, negotiate for, etc. So, these concerns are extremely fresh in my mind!
I went to my interviews probably dressed more professionally than their executives. I went to my first day definitely dressed better than my next two levels of bosses. I think we YLF-types are way more sensitive to how to dress than anyone else around us
You have great style and taste, and just need to get there and work a while and decide what you have that works and what you need to add.
A pair of business casual black work pants (in any fabric you deem worthy) will get you through many days (and no one will notice if you repeat them!)
Your hot commute adds an interesting twist, but my last two weeks have been Austin-like (and you have my sympathy). I found my place actually runs warm, so I unlayer whatever I can, and wait for the AC to kick in before I'll get in the car.
The wait to start is torture though -- I kept shopping and shopping and buying stray things because they just might be right. So, I have more than a few things to return now