Great to counterract the Coolant loss
Some of our cars seem to lose coolant quicker than others in hot weather because of evaporation and such, several forum posts talk about this. This comes in handy at the end of the summer to top off half with the radiator and the rest into the overflow tank. Make sure your doing this with the engine warmed up and the radiator and overflow cap off from the start, and make sure you follow normal procedures to bleed the system if your starting out fresh.