The force has urged the public not to be alarmed, as training exercises will be carried out in Fulford area of York.
A spokesman for the force said: "Our Firearms Unit will be conducting training exercises in the Fulford area of York this evening.
"Please don’t be alarmed if you notice a lot of police activity or if you hear some noise for a short space of time."
How many armed police officers are there in the UK?
Most police in the UK are not routinely armed. Instead, forces rely on specially trained Authorised Firearms Officers (AFOs) to attend incidents where firearms might be needed.
Specialist Firearms Officers are usually trained to a higher standard than an AFO, as they are likely to be the officers entering besieged premises.
The vast majority of firearms used by British police are semi-automatic, and there are regulations governing their use issued by the Association of Chief Police Officers