"...Groundhogs seem to be the most active just after..." Yep. In the summer. Where you are has a lot to do with when ground hogs first come out of hibernation(they're one of the few true hibernators). Up here, in Southern Ontario, Canada, they can be out in the first week of March(Ive shot 'em off snow banks, but not often), depending on the weather. Day time temperatures mostly. Between then and June or July(again depending on temperatures), they'll be out most of a warm sunny day from dawn until dusk. They dislike rain, but will be out briefly on the second consecutive rainy day to eat. Once the temeratures get hot, they'll be out once the dew is off, back underground during the hottest part of the day and out again in the evening. During extremely hot periods, they'll go back into hibernation until things cool off. By the middle of September to the end of the month, they've gone back to bed for the winter.
"...then you can have MONSTER deer..." Yep. Big deer that breed like rabbits. Up there are miles and miles and miles of corn and soy bean fields with some wheat thrown in. There are so many big deer being hit by vehicles the insurance companies are paying millions in damage claims. No natural predators either. Although, we keep hearing about cougars being seen and more black bears(not that they actively hunt deer). Lots of coyotes too. None of which are having the least bit of effect on the deer population.