General Motors (NYSE:GM) stock has been on a roller-coaster ride this year, as investors try to weigh the company's record earnings-per-share performance against falling sales and a persistent inventory glut in the U.S. (Through the end of July, domestic deliveries were down 3.8% at GM, while dealer stocks were a stunning 38% higher than at the end of July 2016.)

Fortunately, the General bounced back with a strong August, outpacing crosstown rival Ford Motor (NYSE:F). Furthermore, both automakers are set to benefit in the coming months from an uptick in vehicle demand due to the severe flooding caused by Hurricane Harvey.

GM's sales jump in August

Last month, General Motors delivered 275,552 vehicles in the U.S.: up 7.5% year over year. This was a nice recovery from the 15.4% decline in deliveries that GM logged in July. Retail sales rose 4.2% year over year in August, while fleet deliveries surged by 24%.

GM's updated crossover lineup is clearly contributing to the company's sales turnaround. The redesigned GMC Acadia midsize crossover -- which hit the market in 2016 for the 2017 model year -- continues to gain traction. U.S. deliveries are up more than 45% year to date, including a 56% gain last month. Meanwhile, deliveries of the new Chevy Equinox -- which hit dealer lots earlier this year -- nearly doubled in August to 28,245 units.

A Chevy Equinox crossover

Redesigned crossover models are key for GM's growth. Image source: General Motors.

Even more recently, redesigned versions of the GMC Terrain and Chevy Traverse crossovers are becoming available. Last month, deliveries of those two models increased 54% and 35% year over year, respectively. (However, most of that volume came from 2017 models being cleared out.)

The combination of strong sales in August along with lower production allowed GM to reduce dealer inventories by nearly 47,000 units last month, to 893,056 units. This makes GM's goal of ending 2017 with dealer stocks in line with the 2016 year-end level of 844,942 units seem quite achievable.

Ford falls short

In contrast to GM, Ford posted a 2.1% drop in its U.S. deliveries for the month of August. Part of this decrease was driven by another deliberate reduction in low-margin sales to rental car companies. However, retail sales were also down by 2.7% year over year.

Ford's extremely profitable F-Series truck lineup is still producing stellar results. Deliveries surged 15% year over year last month, surpassing 77,000 units. U.S. deliveries of F-Series trucks could reach the 900,000 unit mark for just the third time ever during 2017.

However, Ford is becoming too reliant on a single product. The F-Series family accounted for 37% of Ford's deliveries last month (including the upscale Lincoln brand). On the flip side, Ford reported a shocking double-digit decline in crossover deliveries last month. This lends credence to a recent analyst report that warned investors about Ford's weak competitive position in the SUV/crossover market.

Hurricane Harvey could deliver a windfall for automakers

In 2016, U.S. auto sales reached a new all-time high for the second consecutive year. So far, 2017 has been shaping up to be somewhat weaker, with unit sales on pace to decline 2%-3% year over year.

However, automakers are poised to benefit in the coming months from the destruction caused by Hurricane Harvey. The hurricane's arrival undoubtedly hurt auto sales in the last week of August. However, people who lost their vehicles will need to replace them soon.

Indeed, hundreds of thousands of vehicles in the Houston area could be totaled after sitting underwater for days due to widespread flooding. Some estimates put the number of vehicles destroyed as high as 1 million. This is likely to lift U.S. auto sales for the next few months.

GM recently announced new incentives specific to areas impacted by Hurricane Harvey, to help -- and encourage -- people who lost their vehicles to buy new ones. For example, eligible customers who were affected by the storm can defer their first payment by 90 days if they finance a new vehicle purchase through GM Financial.

2017 still won't be quite as good a year as 2016 for GM and its rivals. However, they now have a great opportunity to end the year on a high note.

Adam Levine-Weinberg owns shares of General Motors. The Motley Fool owns shares of and recommends Ford. The Motley Fool has a disclosure policy.