What? My car (which is quite old) has indicator of cold water, and recommends not to drive it till it is gone. It takes 3 minutes of idling in winter for that i

What? My car (which is quite old) has indicator of cold water, and recommends not to drive it till it is gone. It takes 3 minutes of idling in winter for that indicator to be gone. I assume other cars have it too. For that 3 minutes, RPM is high, you can see it at needle and you can hear it too. Once indicator is gone, RPM needle drops and noise becomes lower too.