Does sunlight shine directly into the bay windows? If so, for how long?
If where you are is winter now, I doubt they'd get overheated, especially if sun didn't shine into the windows or if it did, for only a small portion of the day (can't give a more definite answer without knowing the above). Monitoring the water temp and basking area temps are important. You're more likely to have an algae issue, though. And when summer comes, I'd move the tank to a cooler area.
If the main reason for where you want to put the tank is so your turtles can have twilight, know that they don't need it.

"You become responsible, forever, for what you have tamed." -Antoine de Saint Exupery-