This phrase has been in use since the latter part of the 1900s. The origin is not clear.
- - He really didn’t mean what he said about you. He said it in the heat of the moment.
- - He was very stressed and frustrated and in the heat of the moment, quit his job.
- - She had a big argument with her husband and in the heat of the moment, left him.
- - He lost his head in the heat of the moment and tried to hit the police officer.
- - In sports, most offences are actually committed in the heat of the moment. The offenders usually rue their actions later.