Does a warning for speeding issued by a police officer go on my record and if so for how long does it stay on there? I live in Iowa.

Can you elaborate? Was it a warning because the tail lights on your car were out and you have x-number of days to get them fixed?

More info is needed here.

At least in the few states where I was in law enforcement a warning only stays at the local police station, it is not on any state wide system.

It is possible some states have it. But a warning, such as a criminal tresspass warning, telling you not to go back into Walmart, or a warning for speeding, or a warning for running a stop light is written up by the officer on an incident card and may or may not be added to that departments computer data base. But the files are available to have you checked to see if you were warned before.

Now as a officer I used to warn 100's of people "off the books" no card, we called it in as a motorist assist, and just told them to be more careful next time.

And since it is not a ticket, you were not convicted, even if a warning shows up he can not be used against you for insurance or for anything else than to give the officers a reason not to warn you next time.

In the instance of a criminal tresspass warning, it can be used against you, since it is proof you were told not to do something if you do it again,