The forage times for squirrels does change here in Michigan I am guessing due to the weather/cold.
When the days start off around 35F and up they start foraging just after first light and will be out and about nearly all day. When the day temps are starting out in the teens or lower they will be out as soon as the sun breaks around 7:30 AM here till about 10:00AM then are pretty much gone till around 3:00PM for a hour and a half.
Al