A key U.S. industry is sending us a warning.

And it could spell serious trouble ahead for the economy at large.

The good news is that there's still time to protect yourself. I'll show you how to do that at the end of today's essay.

But let's first turn our attention to the struggling industry.

• I'm talking about the auto industry…

Specifically, let's look at vehicle inventories… which are swelling across the nation right now.

We're seeing this firsthand near Casey Research's headquarters in South Florida.

In fact, Casey Research analyst Houston Molnar tells me that he sees this issue every day. Dealership lots are overflowing with unsold cars.

One dealership even started storing vehicles on an undeveloped plot of land across the street, after it ran out of parking space. Another dealership is moving its inventory to the nearby grocery store parking lot.

• But this isn't just happening in South Florida…

According to Bloomberg, the average new car spends 73 days in a dealership's lot before being sold. That's up from 67 days in June.

And experts expect this figure to reach 78 days when data for December 2018 is available. That would represent a 16% increase in just six months.

There's a good chance that happens. I say this because, according to the Federation of Automobile Dealers Association, passenger vehicle inventory jumped nearly 34% from December 2018 to January 2019.

Not only that, Ford's total sales are down 28% over the past year. Hyundai's are down 21%, while Toyota's and Nissan's are down 3% and 2%, respectively.

Of course, there's a reason why dealerships across the nation are struggling to move inventory…

• It's getting more expensive to buy a vehicle…

And that's because interest rates are rising…

In December, the Federal Reserve lifted its key interest rate for the fourth time in 2018… and the sixth time since the start of 2017. This benchmark is now sitting at its highest level since April 2008.