Cramer: Not clear if this is still a bull market

Cramer: This is a very bad market

As a very volatile month comes to a close, investors should take note and realize that this is a "very bad market," CNBC's Jim Cramer said Monday.

"The market's very thin. People are making a lot of big moves in a market that is not that stable, but I would point out that we have to get used to this. [S&P 500] futures were down 25 [points] last night and there was nothing going on," Cramer said on "Squawk on the Street."

An investor in front of an electronic board showing stock information at a brokerage house in Fuyang, China, July 28, 2015.
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Monday was the last trading day in August, and the three major indexes were all down more than 5 percent for the month.

"The carnage has been incredible, and we keep acting in this 'wait until you see what happens' mode. I take a look at the charts and I cannot believe what has happened," Cramer added.

"Is this a bull market? It's not clear to me."

U.S. equities opened trading sharply lower Monday.