The end of summer is almost upon us, but some hot stocks aren't ready to cool off. Hundreds of U.S. stocks scored gains of at least 50% through the first eight months of the year, outperforming the volatile market's ups and downs -- among them, Target (NYSE:TGT), Shopify (NYSE:SHOP)Roku (NASDAQ:ROKU), Momo (NASDAQ:MOMO), and RingCentral (NYSE:RNG).

Here's why all five could keep the good times going for investors in the months ahead. 

Shopify's CEO speaking on a stage alongside Canada's prime minister.

Image source: Shopify.

Target: Up 66% in 2019

A lot of traditional retailers are struggling these days, but Target's store logo apparently remains a bullseye for shoppers. The "cheap chic" retailer is back with a vengeance. Comps climbed 3.4% in its latest quarter, a gain that was stacked on top of a 6.5% pop a year earlier. Put another way, the average store is selling 10% more than it was two years ago.

Digital sales are a major driver of Target's recent growth, but it's also excelling at keeping costs in check. It's expanding its margins, and that's something that you don't see a lot among hungry retailers lately. In addition, adjusted earnings have landed ahead of management's guidance and Wall Street's profit targets for three consecutive quarters. 

Shopify: Up 177%

The internet has made it possible for any business to sell its wares to the world, and Shopify is making that process seamless for its more than 800,000 merchants. Shopify storefronts are everywhere, and even though the company's revenue growth is slowing -- year-over-year upticks have decelerated for 14 consecutive quarters -- it's hard to ignore a dot-com darling that still came through with a 48% top-line surge in its latest quarter.

The stock has nearly tripled this year, and analysts keep raising their price targets to keep up both with the buoyant share price and the business's improving fundamentals. Last week, it was Mark Zgutowicz at Rosenblatt lifting his price goal on the shares to a Wall Street high of $481, excited by the prospects of modest acceleration in gross merchandise volume in the future. 

Roku: Up 412%

If you're kicking yourself for missing out on Shopify this year, just imagine the self-bruising you can put yourself through for failing to cash in on 2019 five-bagger Roku. The streaming TV pioneer's platform has emerged as a rock star in the booming cord-cutting revolution. 

There are now 30.5 million active accounts leaning on Roku, and this quarter, those users should stream more than 10 billion hours of content across the thousands of services available on the platform. Momentum favors the company, and while its share price has outpaced its fundamentals in 2019, betting against Roku has been an easy way to get burned this year.

Momo: Up 55%

Chinese internet stocks may seem an unlikely hotbed for investors' interest in 2019, considering that country's slowing economy and its ongoing trade tussle with the U.S., but Momo is rising above the fray. With its social discovery and online dating sites gaining traction in the world's most populous nation, its revenue climbed 32% in its latest quarter -- and adjusted earnings rose even faster.

A lot of this month's hot stocks trade at pricy multiples, but that's not the case with Momo. Despite its rally, shares can still be had for less than 14 times this year's expected adjusted earnings, and just 11 times next year's bottom-line forecast. 

RingCentral: Up 71% 

Companies need smart phone systems to stay on top of incoming communications, and that's what RingCentral provides with its cloud-based platform that automatically routes inbound calls to whatever device a recipient is using. RingCentral isn't a household name among consumers, but it's proving to be resiliently sticky for its enterprise clients. 

Revenue rose 34% in the second quarter, and the numbers are just as impressive on the other end of the income statement. RingCentral has posted double-digit percentage beats on the bottom line for the past seven quarters. It's been the right call for investors. 

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.