Economist Milton Friedman famously taught us that monetary policy operates with long and variable lags. By this he meant that it takes time for the Federal Reserve’s actions to affect the economy, in much the same way as it takes time for a room’s temperature to adjust to changes in a thermostat’s setting. If the Fed waits for inflation to manifest itself before raising interest rates, it will have waited too long to prevent inflation from becoming a real problem.

(SOURCE) https://www.cnn.com/2022/05/02/perspectives/fed-monetary-policy-interest-rates/index.html