An inverted yield curve is one of the most reliable leading indicators of an ensuing recession.
That is, when longer maturity Treasury yields such as that of 10, 20, or 30-year bonds are lower than the yields of short-term Treasury yields, this signifies the market betting that the Federal Reserve will soon lower the overnight rate. A lower overnight rate will ripple out to lower short-term rates.
It's up for debate whether an inverted yield curve still works well as a leading indicator of economic weakness ahead. Those who say it doesn't have their reasons