from trusty wiki:
As a general rule, Dry Ice will sublimate at a rate of five to ten pounds every 24 hours in a typical ice chest. This sublimation continues from the time of purchase; therefore, pick up Dry Ice as close to the time needed as possible. Bring an ice chest or some other insulated container to hold the Dry Ice and slow the sublimation rate. Dry Ice sublimates faster than regular ice melts but will extend the life of regular ice.
Note to self: open the car windows if you bring it home inside of your vehicle...... carbon dioxide is emitted fomthe dry ice.... not good, will make you dizzy, etc.
more snow = more water