Fresh tariffs amid high inflation are making the Fed’s job uniquely difficult and feeding uncertainty about what to expect for interest rates this year.

The White House on Friday afternoon announced that President Donald Trump’s threatened tariffs will go into effect almost immediately, starting at 12:01 AM Saturday. The tariffs — 25% on all goods from Canada and Mexico, and 10% on all goods from China — are being described as “draconian” and unnece...