Warren Buffett's $344 Billion Warning to Wall Street is Ringing Out Loud and Clear. Should You Buy or Avoid Stocks During the Market's Historically Worst Month?

Sun, Sep 7, 2025, 6:10 PM 5 min read

• Warren Buffett has been a net seller of stocks quarter after quarter for almost three years.

• The billionaire has a strong track record of outperforming the S&P 500.

• 10 stocks we like better than S&P 500 Index ›

No matter what the market is doing, it's a great idea to keep an eye on the moves of Warren Buffett. He's proved his understanding of stocks over time and his ability to translate that into investing success. The top investor has sat at the helm of Berkshire Hathaway for nearly 60 years, and over that time period has helped drive a compounded annual return of about 20%. That far outshines the S&P 500 (SNPINDEX: ^GSPC), which delivered a 10% such return.

And during times of market uncertainty, it's particularly interesting to look to Buffett for guidance. Now may be one of those times -- with the S&P 500 lingering near record highs and as we start off a month that's historically been the worst for investors. What has Buffett been doing in recent times? Well, the investing giant has been a net seller of stocks quarter after quarter for almost three years.

In fact, his moves have resulted in a $344 billion cash pile at Berkshire Hathaway, and this may be seen as a warning to Wall Street that's ringing out loud and clear. Does this mean you should buy or avoid stocks during the potentially difficult month of September? Let's find out.

So, first, let's talk about the month of September. It's been the worst for investors over time, and this trend is confirmed if we look at recent data. Over the past five years, the S&P 500 only advanced once in September -- by 2% last year. The other Septembers resulted in losses of about 3% to 9%. If history is correct, we may be heading for another tough month that could lower the value of your portfolio, at least temporarily.

Now, let's move on to Buffett's warning. The billionaire never joins in big market movements. For example, if everyone is buying artificial intelligence (AI) stocks, Buffett won't be part of this crowd. He doesn't do this just to be contrary. Instead, Buffett prefers focusing on value stocks -- quality companies that may be overlooked by the general market today but have what it takes to deliver growth over the long run.

So, in recent quarters, as investors flocked to technology and growth stocks and the S&P 500 soared, Buffett bought selectively and grew his pile of cash, readying himself for future investment opportunities. Buffett's warning is essentially this: Stocks have become expensive, and as a result, the market could pull back at any moment.