Get set to hear dour numbers when U.S. companies report their earnings for the third quarter. Big banks kick off earnings season Tuesday with JPMorgan Chase, Goldman Sachs, Citigroup, and Wells Fargo on deck. Hurt by falling interest rates, banks' earnings could drop 1.2%, says Refinitive. That would mark the sector's first decline in three years.

Banking aside, the overall picture isn't much brighter. Uncertainty about the economy and the U.S.-China trade war are expected to slam earnings of major U.S. companies. Refinitive says Wall Street analysts see earnings for companies on the S&P 500 sliding 3.2% from a year ago. That would mark the weakest performance in about three years.

Sectors with international exposure will take the biggest hits. Earnings from the tech sector are expected to drop more than 7%, led by chip maker Micron Technology. Also suffering: two sectors that are most exposed to the overall economy and the trade dispute: energy and materials.