Annual Weather Summary: November 2017 to October 2018 Winter will be colder than normal, especially in the south, with the coldest periods from late November into early December and in late December, mid-January, and early February.
It is an adjective that serves to modify nouns. Nouns modified by every are singular and must be written in such a manner. For example: Every <person> involved in the crash died. The reason for this singularity is because the word every literally means each, and refers to a single entity. Moreover, another reason for this is every is derived from the terms everything and everyone.. Notice here that obviously thing and one are singular objects.
People is human beings in general or considered collectively. A person is a human being regarded as an individual.If you are referring to two humans, yes, it would be grammatically correct to say persons. It is definitely a word. It is plural for an individual, but does not refer to a collective group of humans. It could be used in speaking about two humans of a household.