Is the Forbidden City open on Mondays in the Summer?

This website says that the Forbidden City is open on Mondays during the summer vacation period of Jul 1 to Aug 31.
However I am finding conflicting information that is telling me otherwise. One tour group said it is closed on Mondays.

Can you confirm that it is either OPEN or CLOSED on Mondays during July 1 to August 31?

I am making travel plans and I need to know.
Thank you.