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.
In fact, when referring to the quality of genius (as opposed to an individual possessing certain qualities or a certain nature), geniuses is the plural that one should normally use. However, when referring to an individual as a genius, the most correct plural is genii (that's three syllables). This is because genius is derived from Latin. It is the first-person masculine singular form of the word. The first-person masculine plural is genii.