Dont panic yet untill you've checked a few things: was the overflow bottle overfull to start with?
Is the cap OK. On Ford radiators which sit sideways (header tank on rh-end) the cap must have a good seal, other wise coolant will leak out rapidly under pressure.
Is your fan working? Viscous coupling, check for resistance to spinning by hand (engine -off) Are they electric fans? check for operation.
Apart from checking the other basics such as hose clamp and hose condition, only then do you look for more sophsticated faults.
After a hot day with the AC on, all cars will heat-soak after switch off,...some especially if the overflow or coolant recovery bottle is over full to start with will overflow.