However, I have never been one to limit my alcohol consumption based on something as silly as the seasons, so here's the recipe:
1 to 1 to 1 of brandy, an orange liqueur (such as Cointreau, Gran Gala, etc.), and lemon juice. Shake it up till cold, or if you're like me and don't own a cocktail shaker, just stir with a lot of ice until chilly. Easy enough.
It reminds me of a citrusy Manhattan, sans woodiness from the whiskey and medicinal quality from the vermouth and bitters. And I thought, "Hey, sidecar + fizz = a totally summer-acceptable libation!"
So, try it. Make a small one to try, and then add some seltzer water. It's refreshing, very lemony (if you don't do tangy, cut back on the lemon juice, obv., but don't cut back too much), boozy, and now I have to think up a good name. Best enjoyed near a pool while wearing huge sunglasses and an even larger hat.
I'll get back to you on the name when something strikes me... :)