There was a recent post on Tumblr about an 8th grade girl being told to roll her shirt down to avoid exposing her midriff during a field day in 85+ degree Fahrenheit weather (it was a sunny day, so the temperature was likely in the 90s despite the atmospheric reading), while the boys were allowed to practically undress.
Someone began flipping out at me for disagreeing with her (ironically, I think she's one of the more prominent female Tumblr MLP fans) about her statement that "Nobody should have exposed themselves in the first place" because it's "unprofessional" and we need to teach our kids that they need to dress appropriately and cover themselves as adults.
Bitch, I live in Florida. It was 93 today, minus the heat provided by the shining sun that turned me as brown as Kanye West in two days. People around here have no problems wearing Daisy Dukes and rolling up or even removing their shirts to avoid overheating. Quite a few work environments, especially ones that have you outside in 90+ degree weather, relax their dress code for the comfort of their employees. Even the military, the most infamously hardass job there is, lets its soldiers partially undress when they're working in a hot climate. They actually understand the threat provided by extremes of temperature, and often don't force the soldiers to wear full clothes and gear unless they're necessary for the protection.
The whole reason this "standard" exists is because we live in a society that continues to tell us that our bodies are a private, shameful thing that must be hidden, and we still teach our kids (especially boys) that exposed shoulders, stomachs, and bra straps are titillating and indecent in public. It has nothing to do with "being professional" and "having standards" and everything to do with society oversexualizing and shaming the human body.