Title says it all…
Perfect Day by Lou Reed?
The Lark Ascending.
(I don’t live in town)
“Good Day Sunshine” by The Beatles
“Groovin’” by The Young Rascals (for tomorrow)
Around here, today, it’s been a Rainy Day in June.
(The link is to the Kinks song. I didn’t realize until now, googling it, that there’s also an Alan Jackson song by that name.)
That Sunday, That Summer by Nat King Cole.
“Lovely Day,” Bill Withers
Hot Fun in the Summertime, Sly and the Family Stone
Summertime, Summertime, The Jamies
“Summer Wind” of course.
Tip Toe Through the Tulips, by Tiny Tim 
Good song for sunset at the end of a perfect summer day: the theme fromEndless Summer.
Eric Johnson’s “Cliffs of Dover”.
Makes me want to hop in the convertible* and just ride the highways on a summer day.*I don’t have a convertible.
Summer Breeze by Seals and Crofts.
“Mr. E’s Beautiful Blues”-eels (NSFW lyrics)