We have some exciting news to share! The Motley Fool UK has now become The Twelfth Magpie -- an independent, UK-owned company, led by our long-serving UK management team — Mark Rogers, Chris Nials and Heather Adlington. In practical terms, it’s the same team you know, now fully focused on serving our UK readers and members.

Just as importantly, our approach remains unchanged: long-term, jargon-free, and on your side. This site is our new home, and there will be extra tweaks made across the coming few days as we settle in. So if anything looks a little off, please bear with us!

The content of this article was relevant at the time of publishing. Circumstances change continuously and caution should therefore be exercised when relying upon any content contained within this article.

3 reasons the US stock market could crash in September 2025

Some major red flags are emerging in the US stock market that could trigger a crash at the end of summer, but what can investors do to prepare?

| More on:
British pound data

Image source: Getty Images

You’re reading a free article with opinions that may differ from The Motley Fool’s Premium Investing Services. Become a Motley Fool member today to get instant access to our top analyst recommendations, in-depth research, investing resources, and more. Learn More.

The US stock market’s close to another all-time high, at least when looking at the S&P 500 index. That’s terrific for anyone who’s been snapping up shares in recent years.

However, despite the seemingly strong investor sentiment, there are some potentially massive risks being overlooked, several of which could even trigger a full blown crash later this year.

XXX

Major red flags

There are several concerning trends that the market is seemingly ignoring. I think the three biggest are:

1. Rich/fragile valuations

The investment management company Pimco has recently calculated the cyclically adjusted price-to-earnings (CAPE) ratio of the S&P 500 to be in the 94th percentile. That’s a fancy way of saying US stocks are trading at earnings multiples significantly higher than their historical average. And historically, such a high CAPE has been a prelude to major market crashes as in 1987 and 2000.

2. Inflation

At the same time, new tax cuts and higher government spending in the US during a time of fiscal instability and tariff uncertainty create a lot of complications for the Federal Reserve. With fears of inflation potentially making a comeback, the central bank could be forced to start hiking interest rates again. And that might spark a fresh wave of corporate defaults given the growing bubble of overleveraged balance sheets.

3. Geopolitical tensions

Beyond brewing trade wars, conflicts have started popping up across the globe, particularly in Eastern Europe and the Middle East. Continued escalation of tensions could lead to even further supply chain disruptions, oil price shocks, or a capital migration to gold, which could spark significant volatility in the stock market – particularly among the businesses trading at lofty valuations.

How to prepare

As we approach the end of summer, the impact of current macroeconomic uncertainties is expected to emerge. That means September could be the tipping point. Does that mean a crash is guaranteed to happen? Of course not. Geopolitical tensions could calm while economist forecasts could be completely wrong (it wouldn’t be the first time).

So what should investors do? Trying to time the market is a strategy that almost never works. Instead, holding through the storm has been a far more successful strategy in the past. Having said that, trimming large portfolio positions might be prudent, especially if the stocks are trading at a lofty valuation.

Take Nvidia (NASDAQ:NVDA) as an example. The GPU chip designer has been one of the best-performing US stocks over the last five years, thanks to skyrocketing demand for its technology. The explosion of artificial intelligence (AI) infrastructure investments by data centres has translated into triple-digit profit growth, propelling the market-cap well beyond $3trn.

However, economic turbulence from the macro-environment could cause AI-related spending to slow significantly. That could potentially wipe out a significant chunk of its income stream. In such a scenario, a sharp share price drop wouldn’t be surprising – especially for a company operating in the cyclical semiconductor space. That’s why investors with a large position in Nvidia today may want to consider potentially trimming their exposure.

If a crash does emerge, there are going to be some fantastic, high-quality companies going on sale. And by having a watchlist to top up on top-notch stocks, investors can be ready to consider incoming bargains like (possibly) Nvidia if they’re not already invested.

Zaven Boyrazian has no position in any of the shares mentioned. The Motley Fool UK has recommended Nvidia. Views expressed on the companies mentioned in this article are those of the writer and therefore may differ from the official recommendations we make in our subscription services such as Share Advisor, Hidden Winners and Pro. Here at The Motley Fool we believe that considering a diverse range of insights makes us better investors.

More on Investing Articles

Friends and sisters exploring the outdoors together in Cornwall. They are standing with their arms around each other at the coast.
Investing Articles

£503 buys 14 shares in this FTSE 250 stock that returned 23.9% annually for the last 15 years

This FTSE 250 stock has averaged a huge return for 15 years. At today's price, £503 buys 14 shares. But…

Read more »

Black woman using loudspeaker to be heard
Investing Articles

£1,000 buys 25 shares in this FTSE 100 stock that’s returned 29.2% annually for the last 10 years

This FTSE 100 mining stock has returned close to 30% a year for a decade. At 3,995p, £1,000 buys 25…

Read more »

Female student sitting at the steps and using laptop
Investing Articles

Down 47%, is this growth stock finally worth buying in May?

With a £288m order book and a hidden pipeline of defence and nuclear contracts, is this growth stock now too…

Read more »

House models and one with REIT - standing for real estate investment trust - written on it.
Investing Articles

2 REITs yielding 7%+ to consider for passive income in 2026

A REIT backed by the NHS and another backed by Tesco and Sainsbury's with both yielding 7%+. Here's why I'm…

Read more »

Woman riding her old fashioned bicycle along the Beach Esplanade at Aberdeen, Scotland.
Investing Articles

Just 97 shares of this UK dividend stock generate £238 in passive income

A 5.7% yield, £238 in passive income from just 97 shares, and one of the most divisive dividend stocks on…

Read more »

ISA coins
Investing Articles

£10,000 in an ISA generates a second income of…

The London Stock Exchange is home to some of the world's most generous dividends. But how big a second income…

Read more »

Shot of a senior man drinking coffee and looking thoughtfully out of a window
Investing Articles

Expert recommendations: 2 top income stocks yielding 7%+!

With yields of 7.2% and 7.8% respectively, these two income stocks are catching the eyes of institutional analysts. Should investors…

Read more »

Illustration of flames over a black background
Investing Articles

3 top income-focused stocks to buy in May 2026, according to experts

Looking for a stock to buy for income in May 2026? Experts have flagged these three UK dividend shares as…

Read more »