What will happen to my car with no antifreeze?

its supposed to freeze tonight and snow tomorrow. it will be in the low twenties tomorrow night. i only have water in my car...no antifreeze.
what will happen?
Update: sorry to sound so dumb...but i really never think about this stuff...i guess im screwed. i cant go to the store, i have 3 sleeping kids! their sorry father should have told me. i specifically asked him earlier if i needed it. he didnt even answer me. oh well, i guess its my own fault for being stupid, but i didnt... show more sorry to sound so dumb...but i really never think about this stuff...i guess im screwed. i cant go to the store, i have 3 sleeping kids! their sorry father should have told me. i specifically asked him earlier if i needed it. he didnt even answer me.
oh well, i guess its my own fault for being stupid, but i didnt even have the money to get any which is why i was asking him.
Update 2: lol...i swear i did not know.
only now am i realizing how incredibly dumb i am.
well... i have been driving for 10 yrs and only put antifreeze in one of my cars...that was last yr,and thats b/c i had the radiador flushed or something...i honestly dont remember.
Update 3: im up all night with my baby anyway...i'll go start it up every few hours...thanks
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