It's a little breezy up there...

^^FWIW, the Giant Wheel was open on Saturday night.

Yeah, I didn't walk in that direction again after it would have opened.

So by Raptors Maunal it can not send empty trains in winds over 25 mph. In the morning they have to send empties to properly test run the ride. The ride can roll backwords from the block if the winds off the bay are to high. Temperature also plays a big role on how fast the trains go. On Saturday there were two times Magnum almost rolled back loaded with guests off its second hill. Typically magnum has problems when the wind is blowing off the lake but becasue of all the conditions (hail, very high wind at 55 mph, the cold, ect.) it was slowing down even with the winds off the bay.

I understand the wind-factor but what is it about the cold that makes coasters slower?

The lubricant (grease) in the wheels is more viscous (thicker) at colder temperatures, so it takes more energy to make the wheels spin. Its not so bad once the trains have warmed up a bit and if the ops can keep them running consistently.
This is also why water dummies or sand bags are thrown into trains early in the day, since a lot of the trains potential energy is used in getting the wheels to move, the dummies help by giving the train more PE.