There are too many unknowns about the worsening coronavirus outbreak to start buying stocks after Monday's worst market slide since October, CNBC's Jim Cramer said Tuesday.

Wall Street opened higher Tuesday, partially rebounding from Monday's more than 450-point drop in the Dow Jones Industrial Average.

"I just think you're coming in on quicksand here," Cramer said on "Squawk Box," as U.S. stock futures were moving higher. "If we had any sort of clarity at all, I would certainly feel like a bounce can happen."

The only things that have happened between Monday and Tuesday, he said, were a dramatic increase in confirmed cases of the new coronavirus in China and a rise in the death toll. Chinese Health officials said that nearly 4,700 people there have been infected and 106 of them have died.

When stocks were sinking Monday, Cramer warned investors who had been waiting for a cheaper entry into the market to wait a little longer.

"This is the panic people have been waiting for," Cramer said as Monday's severe market drop was building. He said then, "I just don't think today" is the day to buy broadly.

Cramer stuck with that advice Tuesday, reiterating concern about a possible "second leg" down for the stock market if the World Health Organization were to declare the coronavirus a global emergency.

"I think when the WHO gets in there we got to prepare for them calling it a pandemic," Cramer said. If that were to happen, "all this rally disappears," the "Mad Money" host warned.