I used to start my days going through all my spam in the morning. It is amazing how much spam is sent over night so as to be right there waiting for you in the morning.
It sort of makes sense that they would do the mass mailings overnight as this is when most computers are taking a break from all that daytime surfing. Then they don’t overload email servers as much.
So, just in case you were wondering why you were getting so much in the morning, that would be my guess (I would love to interview a spammer and find out why they actually do things).