For craft brewers, cooler weather brings a shift in seasonal styles. Gone are the crisp, light, refreshing beers of summer, making way for more malty and spiced brews.

Fall beers are the most popular seasonal style, thanks to the popularity of Oktoberfest brews, wet hops and pumpkin flavors. Look no farther than the annual Great American Beer Festival, underway through Saturday in Denver, where thousands of U.S. craft brewers offer samplings of numerous fall brews.

Tim Hawn, brewmaster for Dogfish Head brewery, pours beers at the 2013 Great American Beer Festival.

Some the best and most creative beers are released this time of year. So throw on that hoodie and try a new fall brew to celebrate the season.

Here are 12 standouts:

Pumpkin beers

For better or worse, pumpkin beers have become the top-selling seasonal style among craft-beer drinkers. During the fall months they're even close to bumping India pale ales (IPAs) out of the top spot of most popular beer style. Spices like clove, nutmeg and allspice are commonly used in these brews, along with orange gourds.

Heavy Seas Brewing Great'er Pumpkin

Baltimore's Heavy Seas has one of the most flavorful and most powerful pumpkin beers out there. Adding to the pumpkin-spice flavors are oak, vanilla and bourbon -- thanks to the aging of the beer in bourbon barrels.

Dogfish Head Brewing Punkin Ale

Dogfish Head, a leader in creative beer flavors, was doing pumpkin beer way before pumpkin beer was cool. Their Punkin is a spiced-up brown ale brewed with pumpkin, brown sugar and spices. This is the gold standard of the style and a true fall classic.

NoDa Brewing Gordgeous

Gordgeous' unique spice character makes this a special offering from NoDa, a Charlotte, North Carolina, brewery. They add fresh spices just prior to brewing, so this beer not only looks good but tastes great, too. Previously available only on draft, Gordgeous now comes in cans for easier home consumption.

Schlafly Brewing Pumpkin Ale

This is a sweetly balanced beer that tastes like pumpkin pie. It's probably one of the most sought-after pumpkin beers, and for good reason.

Oktoberfest beers

If pumpkin is not your thing, and believe me there are tons of you out there, fall still has some pretty good things for you. For one, it's also Oktoberfest season. The famed German festival features malty dark lagers called Märzens, but if you can't make it to Munich for the big party, don't worry -- plenty of craft brewers are serving up their own interpretations of the style.

Sierra Nevada Brewing Oktoberfest

Sierra Nevada joined the Oktoberfest party this year with a unique collaboration with the German brewer Brauhaus Riegele, one of the six brewers that serve beers at the official Oktoberfest in Germany. Each year going forward, Sierra Nevada will partner with another German brewery for their fest beer offering.

Upland Brewing Oktoberfest

This Indiana brewery is making really good beer these days, and their Oktoberfest is one of the best. While it's on the lighter side for an Oktoberfest beer, it's prominent hops make it nicely balanced. Other tasty offerings from Upland include their Wheat Ale and Teddy Bear Kisses, a Russian imperial porter aged on cocoa nibs.

Stoudts Brewing OktoberFest

Stoudts Brewing has been quietly brewing great beer since 1987. The Pennsylvania brewery was co-founded by Carol Stoudt, a legend in the brewing community and the first woman to open a brewery since Prohibition. Their Oktoberfest celebration is one of the best in the country, and their Oktoberfest beer is an excellent, easy-drinking companion to the event.

Revolution Brewing Oktoberfest

Chicago has a rich German heritage, and Revolution Brewing honors that with their Oktoberfest offering. They use all German malts in this one, along with German Hallertau Gold hops. After a few sips you may be "twisting and shouting" like Ferris Bueller.

Hop harvest

At the end of August, the hop fields of the Pacific Northwest are full of ripe hop cones ready for harvesting. The majority of those hops -- used for bitterness, flavor and aroma -- are harvested and preserved. But some hops are set aside within 24 hours of harvest to be used in "wet hop" ales. Compared to preserved hops, fresh-cut hops add a more vibrant, earthy flavor and aroma.

Deschutes Brewing Hop Trip

The folks at Deschutes bag and brew their hops within four hours for this bright, citrusy pale ale. Luckily for them, their brewery is in the middle of Oregon's hop-growing country. For you hopheads, Hop Trip features Nugget, Centennial and Fresh Crystal hops along with some added spices (hey, it's fall).

Sierra Nevada Harvest Wet Hop IPA

Fresh, wet Centennial and Cascade hops give this balanced beer some citrus and herbal notes, but they're not overpowering. Pine and grassy notes also crop up at the end, but the sweetness from the malts calm things down a bit. Sierra Nevada has been at the forefront of using wet hops and releases several fresh hop beers a year.

Founders Brewing Harvest Ale

This is a brilliantly juiced-up IPA with intense pine and tropical fruit flavor. The fresh hops, some of them harvested from Founders' native Michigan, shine all the way through to the finish.

Chatoe Rogue Wet Hop Ale

This year's wet hop ale from Oregon's Rogue brewery is something special. It's brewmaster John Maier's 19,000th beer for Rogue (one of which was a beer made with yeast from his beard). Don't worry, there's no beard yeast in this one -- just Yaquina hops from Rogue's farms, which are tossed in the brew kettle within five hours of picking.