99 Ford Windstar. I kept water in all summer or else it ran hot. Been trying to get antifreeze in through the top because I had no money to pay to find and fix problem, now since cooler outside, water wont go down for me to get antifreeze in.
Adding antifreeze to water in your radiator will not make it run hot, unless you are have a very high portion of antifreeze to water. Antifreeze/coolant raises the boiling point of water to keep it from boiling out and lowers the freezing point to keep it from freezing up.
If it is full of water now and there is no room for antifreeze. Then drain the radiator and refill with the correct mixture of antifreeze and water. This should not only help your cooling issue but also will prevent it from freezing up.
As to the current state of your car, if it is parked near a building or somewhere that might prevent it from being as cold, you might be ok. In any case start it and don't drive anywhere until it has proven that it can maintain a solid temperature.