As the steamy days of summer roll on, fruity sour beers are a good way to beat the heat.

The old-fashioned way to make beer sour involves a monthslong fermentation with a varied mix of wild yeasts and bacteria. This process results in beers of extraordinary complexity, with endless layers of sourness and funk that deliver a different experience with every sip.

The modern method is called "kettle souring," and is how most sour beers on store shelves today are made. The unboiled wort is fermented overnight by a single strain of lactic acid producing bacteria, then boiled. The brewing and fermentation process continue as they would for any other beer.

The result is light, crisp and usually very tart beer, though often fairly one note. But when flavored with fruits, hops and a variety of other ingredients, they become deliciously refreshing beers.

A great place to start with these is Lucy, a moderately tart, year-round offering from Indeed Brewing Co. This wheat-based beer is flavored with lemongrass, bitter orange peel, passion fruit and hop oils. It bursts with hop-like lemon, tangerine, orange and tropical fruit aromas and flavors. The bitterness is sturdier than many kettle-soured beers, giving it a strong impression of dryness in the finish. A touch of bready malt balances the sourness. It's a bit like a lightly sour American pale ale.

For something much bolder, try Coastal Sunshine from Humble Forager Brewery in Waunakee, Wis. Sunshine is an apt descriptor. This beer takes the fruit over the top. Made with passion fruit, mango, guava and pineapple, it's like a rich, tropical fruit smoothie. It appears viscous when poured into a glass and has a mouthfeel to match. A fairly high level of sourness helps to cut through the pulp. At 6% alcohol, it packs a stronger punch than most of these beers. But that flood of tropical fruit makes it a great end-of-the-day treat.

On the far opposite end of the spectrum is Sippin' Pretty from Odell Brewing Co. This one is so light that I put it just a notch above the popular alcoholic fizzy water drinks like White Claw. It has an inexplicable but pleasant steamed rice aroma similar to sake. The a├žai, guava and elderberry in the recipe come out strong in the flavor. An addition of Himalayan pink sea salt gives just the faintest hint of salinity. The finish is short, clean, dry and oh-so-refreshing.

Pryes Brewing Company's Royal Raspberry is about as straightforward as it gets. It's a no-nonsense, medium-sour ale with notes of lemon juice, lemon peel and plenty of tart raspberry. The fruit sits comfortably on a bed of white-bread wheat. Simple, delicious and a great break from the heat.

Every beer that Sierra Nevada Brewing Co. makes is guaranteed to be great, and Wild Little Thing sour ale is no exception. Fruit is king in this watermelon-pink beer brewed with guava, strawberry and hibiscus. Strawberry is a difficult flavor to infuse into beer, but somehow Sierra Nevada managed. It comes in clear from start to finish, with mango filling in the middle. Hibiscus works more to enhance the sourness than appearing as a distinct flavor. With moderate sourness, Wild Little Thing is way too easy to drink way too fast.

Is there anything cooler than cucumber? Oregon's 10-Barrel Brewing Co. is betting not with its Cucumber Crush. This is cucumber salad in crushable beer form. While this may seem to some an odd ingredient for beer, it really works. Lemony tartness is not over the top and does a great job complementing the cucumber. If you enjoy water with cucumber and lemon slices, then you'll love this beer.

Passion fruit Gose (pronounced GO-zuh) is part of the Tanker Truck series of kettle-soured beers from Two Roads Brewing Co. in Stratford, Conn. High lactic sourness blends with lush tropical fruit, with juicy passion fruit being the dominant note. A subtle base of bready wheat and light sweetness helps enhance the fruit and just barely balances the sour. A gose is typically brewed with salt, but it's not perceptible in this beer. It finishes quick, with lingering acidity and passion fruit.

One beer worth a mention is not a kettle-soured beer at all. Sour IPA from New Belgium Brewing Co. is part of the brewery's extensive wood-aging program. Although there is no fruit in the beer, its flavor is all about fruit. Hops and wild fermentation bring a cornucopia of tropical fruits and citrus. Pineapple, passion fruit, grapefruit and lemon all blend together seamlessly. The low bitterness of the hazy IPA offers a perfect counterpoint to the lactic acid tartness. There is a faint hint of barnyard, especially in the finish.

Michael Agnew is a certified cicerone (beer-world version of sommelier) and owner of A Perfect Pint. He can be reached at