My cage is set up by a window. As long as the blinds are shut no light gets in. Is it ok to let sun hit the cage from the window as long as the temperature in the tank doesn't raise, or should I just leave the blinds closed at all times?
As long as the temperature doesn't raise too high, it shouldn't be a problem. They won't gain any UV rays through the glass though. My girls tank gets the late afternoon sun, so the heat concentration is not so high. I would definitely monitor it if you do.
I agree. You'll want to monitor temperatures VERY carefully. The light from the window can provide some beneficial UVA but can also raise the temps in a tank on short notice. I'd be sure to have plenty of ventilation in the enclosure and provide plenty of shady areas to allow for as much temperature variation as possible.