The Collaborative International Dictionary of English v.0.48:
Sunniness \Sun"ni*ness\, n. The quality or state of being sunny. [1913 Webster]WordNet (r) 3.0 (2006):
sunniness n 1: lightness created by sunlight 2: the quality of being cheerful and dispelling gloom; "flowers added a note of cheerfulness to the drab room" [syn: cheerfulness, cheer, sunniness, sunshine] [ant: uncheerfulness]