Closed today

After a few beautiful warm, sunny days with temperatures in the mid teens, today's polar air lowered the temperatures to around 5 degrees.  Yesterday I noticed how wide open the tulip flowers were, the red one in the foreground in particular was wide open, today's photo shows a different story.  It appears that temperature as well as light is a factor that causes the flowers to open and close, opening when warm to allow the insects in to pollinate, and closing when dark and damp to prevent the pollen from being damaged.