Ground-hog Day takes place in February in the North Eastern part of the Unites States, yet every morning Bill Murray wakes up at 6:00 am and finds it to be light as day outside. Realistically, in the middle of winter, we wouldn't see the sun rise until at least 7:00 am.
That is very true... it's odd that something so obvious could have gone unnoticed. Still, it is possible that they knew this but wanted the audience/viewers to be able to see what it looked like each time he got up in the morning without having to turn on the lights every time. Far-fetched, but possible.