I love both simple and fruit-based drinks in the summer. A gin and tonic is always fine and a Negroni is good in any weather. Hendricks please for that Negroni and a touch of Cucumber Crop vodka for my G&T would be fine, thanks.
So if those don't always fit the bill here are another couple of suggestions to beat the heat (even if you don't really need to in San Francisco):

NAVAN Watermelon Daiquiri:
Ingredients:
.5 ounce NAVAN
1 ounce 10 Cane Rum (or other, light, white rums)
3 chunks watermelon
.5 ounce simple syrup
.25 ounce lemon juice
Instructions: Muddle the watermelon in the bottom of a mixing glass. Add the other ingredients. Shake and strain into a chilled Martini glass. Garnish with a seeded watermelon slice.
Daiquiri (no blender needed):
Ingredients:
3 parts rum of your choice (I love dark rum)
1 part lime or lemon juice
1/2 part sugar
Instructions: In a shaker with ice, combine ingredients. Shake and pour into glass.
Cheers,
Liza the Wine Chick