Summer calls for light scents, there is nothing new about that. It seems that the most summery scents divide into the following four categories:

Citrus

There is something about the rind of citrus fruit makes most people feel rejuvenated and refreshed. Citrus oils have been in use in many toiletries due to their anti-bacterial properties, and therefore are associated with cleanliness and purity. For many, a citrus cologne is all they can take in the summer. An even funner way to enjoy your citrus fragrances, especially if you live in the tropics or the desert is to refrigerate the cologne and enjoy a double-cool splash of citrus throughout the day.
Although I've never been much of a citrus wearer personally, I do enjoy the lemony bite of Le Parfum de Therese, Eau Sauvage, O de Lancome (all are Chypre-Citrus of sorts)and my very own ArbitRary & Fetish.

Dry Woody

Dryness in the sense of un-sweet and non-cloying is a desired effect when heat and humidity reign. The note of vetiver is particularly effective in that regard. They have been considered cooling in Ayurvedic medicine for hundreds if not thousands of years. In the tropical countries where vetiver grows wild, vetiver rootlets are woven into mats, blinds and fans. When moistened with water, they release their cooling, clean-woody and earthy-sweet scent and create a calm, grounded feeling. When the wind comes through the moist blinds this aroma enters the home and relieves the dwelles from the heat. A wood fan scented with sandalwood or agarwood (I found mine in Chinatown and am just grateful for their aroma and design when I travel to my air-conditionered home-village). A woven vetiver-root fan can be found at Samara Botane and in the summer they sometime also offer vetiver hydrosol which can be sprinkled on the fan for an extra vetiver boost.

My favourites of the vetiver genre are Vetiver Tonka, Guerlain's Vetiver, Vetiver Extraordinaire and my own , Sabotage & Vetiver Racinettes. On the more woody side, Bon Zai and Philosykos have that tingling fresh dryness that is so rejuvenating when there is no fan to be seen.

Beachy

Beach-summer association requires no explanations. Suntan lotions, vanilla ice cream cones, coconut oil and the scent of sun warmed sun and skin are for most people the epitome of summer’s olfactory symbols. Any scent that would even vaguely remind us of these sensual and lazy experiences is welcome in summertime (or when sunshine is missed here on the northern West Coast!). Azuree Body Oil (or Bronze Goddess, if you will) Fire Island's sun-tan lotion sans the grease, or chocolate-dipped banana ice-cream bar, also know as Vanille-Banane (or for that matter, take a pick from any of the Comptoir Sud Pacifique line and you'll be sucked into one beach fantasy or another).
And from my own creations the beachiest are Coralle & Gigi.

Tropical Floral