Here comes Citi...

Citi is expected to report Q2 earnings at 8 a.m. ET Friday.

Analysts are expecting adjusted earnings per share of $1.10 on revenue of $17.56 billion, according to Bloomberg.

Total trading revenue is expected to come in at $5.16 billion, according to a Bloomberg survey of analysts, while investment banking revenue is expected to be $1.49 billion.

In the same quarter last year, Citi reported earnings per share of $1.45 on revenue of $19.5 billion ($18.81 billion expected.)

In the first quarter, that beat expectations despite a major profit drop. The firm reported adjusted earnings per share of $1.10 ($1.05 expected) on revenues of $17.55 billion ($17.53 billion expected).

"While our market-sensitive products clearly suffered from weak investor sentiment during the quarter, we continued to make progress in several key areas," CEO Michael Corbat said in a statement at the time.

The big story during the second quarter was the UK's decision in June to leave the European Union, which sent shockwaves through markets and could deter central banks from raising interest rates anytime soon.

In the short term, that could be good news for banks' trading revenues, but the long term impacts are less rosy. Bank profitability is largely based on the rate at which they make loans. Lower global interest rates, in turn, negatively affect bank bottom lines.

JPMorgan reported Q2 earnings on Thursday, beating expectations. Wells Fargo is also expected to report Friday morning. Bank of America Merrill Lynch will report Monday, Goldman Sachs Tuesday, and Morgan Stanley Wednesday.