How could I simulate a winter's chill on an outdoor plant?

[gary in santa cruz]

My climate is right on the edge of being cold enough to support blueberries. If I could only simulate being in a colder climate, the plant would do much better. How could I simulate 10 days of near freezing weather? The only idea I have, is to create a portable cooler shell to place around the plant (2 feet tall), and put bags of ice inside.
thank you for any ideas!