We have all been there. A long work day that is followed by an event or a happy hour with friends. You do not want to nor do you the time to go home and change so your best bet is to just freshen up after work. There is a fool proof system in making that transition seamlessly in the summer.
Wear flats and change into heels.
Give your feet a break during the day. There is a good chance that whatever your after work plans are, they will involve more standing than you do at the office. So, stick to flats during the day and then change into your heels. It will also be a way of giving you a fresh night time look.
Wear a blazer or denim jacket to keep things office appropriate.
My company is pretty liberal with dress code, but that is not the same across the board. For that reason, throw on a blazer or denim jacket that coordinates with your look. With the air conditioning that is probably pumping in your office, you will be grateful to have that blazer anyway.
Do not change your outfit entirely.
Obviously this your prerogative, but it is so much easier to just have a core outfit with interchangeable accessories ( i.e.: flats to heels). To bring an entirely new outfit to change into is too complicated. Keep things simple. You will see that in just changing your accessories, you will see a world of difference.
Optional: Add a bold lip at night.
A great way to take your look from day to night is by adding statement lip color. I personally wear lipstick all day, but if you are the type of girl who reserves lipstick for night time activities this is an opportunity to do it!