Here's a picture that I actually took by mistake while adjusting my camera settings. Once I saw it, I decided to keep it, because it just seemed to scream SUMMERTIME to me!
Bare feet, green grass, sand buckets, flip flops, and beach towel... Does it get any more summer than that?
(My boys and I were at the lake with our neighbor and her kiddos the other day when I 'snapped' this photo!)