"It's getting to the point where you can set your clock to it," read a Tuesday report by Bespoke Investment Group.

What's the market analysis firm referring to? Selling stocks when the yield on the 10-year U.S. Treasury reaches 3%. 

And that's been the case this week. According to Bespoke, during 2022, every time the 10-year U.S. Treasury yields climb to 3% or above, the S&P 500 goes into bear mode for weeks in a row. The event occurred twice this year already.

Understanding Treasury Yield, Stock Prices Relationship: The U.S. government borrows money from investors in the form of Treasury bonds, which yield specific interest rates depending on the bond's time frame.

Since the bonds can then be resold in the secondary market, the price of the bonds themselves changes according to supply and demand. If an investor buys a bond at a cheaper price than it was originally sold, the yield grows because the U.S. government still has to pay up the same yield rate at which the bond was originally sold to the first buyer.

Why Are Investors Selling Bonds? The price of Treasury bonds is going down now (bringing yields up) because investors have been getting rid of bonds in anticipation of the Federal Reserve's annual symposium in Jackson Hole, Wyoming, which begins Thursday, as reported by Insider.

On Friday, Jerome Powell, the Federal Reserve chair, is expected to give a speech addressing the Fed's strategies for taming inflation, which could include an even more aggressive raise to the federal funds rate, which is already at 2.5% and could hit 3% by the end of the year.

As interest rates go up, the value of bonds usually goes down, bringing up yields.

The $S&P 500 index (.SPX.US)$ fell twice this year after the 10-year Treasury bond yield touched 3%. Once in May, when it dropped 5% in one week, and another in June, when it fell 9% in one week and then another 7% in the following month.

If Powell effectively announces higher interest rates for the rest of the year, the value of bonds will keep on dropping, driving up yields and thus causing other investors to sell their stocks in favor of bonds, bringing down the stock market as a consequence.