Stocks closed higher on Wall Street, giving the market its fifth gain in a row and notching another record high for the Dow Jones Industrial Average.

In overseas markets, Europe's Stoxx 600 pared gains following the PMI data and was last marked 0.3% higher in midday Frankfurt trading. Britain's FTSE 100, meanwhile, rose 0.74% as the pound fell to a six-month low of 1.2521 against the surging U.S. dollar.

This Fed-based market signal is flashing a warning for the first time in over a decade. Here’s why it matters.