A Muslim can go to a temple if a need arises as long as he does not participate in the pagan rituals they perform. There is nothing in Islam worse than idolatry.

Therefore, if you are going there for volunteering for a particular project involving soup kitchen or feeding the poor, etc., there is nothing objectionable. It would be a good work meriting rewards in the sight of Allah.

We may do well to remember that the Prophet (peace be upon him) and his companions participated in all of the good works done by the Quraysh in the Haram who were pagans and used to serve as the custodians of the Kab’ah which was full of idols before they converted to Islam.