I calculated average at winter , spring, summer and autumn periods of one factor with two levels (A and B). I added  the average of each level to get annual value:

Aan =  ( Average of winter + Average of spring + Average of summer + average     of   autumn

Ban = ( Average of winter + Average of spring + Average of summer + average of autumn

Please, see the attached file

How to know if Aan and Ban are significantly different or are not?