A friend made this drink for us one hot night many Julys ago. He dubbed it the "Liberator," and whenever the humidity and temperature hit the 90/90 mark, we liberate ourselves by mixing up a few.
It couldn't be much easier. Squeeze half of a juicy lime into the bottom of a large cocktail glass. Add about a teaspoon of sugar, and stir to mix. Fill the glass with ice and add one to one and a half ounces of rum, depending on the degree of liberation you wish to attain. Top it off with tonic water, and garnish with a wedge of lime.
If you like your drinks a little tart, like Tim does, use a whole lime's worth of juice. If you like your drinks a little sweeter, like Ruth does, put in two teaspoons of sugar.
On that muggy night many years ago, our friend used a couple of tablespoons of frozen lime juice instead of fresh, and that worked fine too.
Enjoy on the deck with friends, pets, snacks, and bug spray.