The S&P 500 was up more than 40%, as of Tuesday's close, from its March 23 intraday bottom, a rally that Cramer called one of the "greatest moves of my lifetime."
"I'm not advocating that this is a 'get-out-now' moment. I just think we've had such a good run," Cramer said on "Squawk on the Street." "There's so many signs that we're getting, why not obey some of them and go and take a little off, and maybe you can say, 'I took some off before something bad happened.'"
Cramer's comments came shortly before Wednesday's open on Wall Street, which saw the Dow Jones Industrial Average sink on worries about growing Covid-19 cases in states such as Texas, Arizona and California.
Uncertainty about the virus and its economic consequences devastated financial markets beginning in February, before Federal Reserve action, fiscal stimulus and hopes for a strong economic rebound ignited a swift rally in equity prices.
Cramer, host of "Mad Money," stressed that investors who have seen gains in their portfolio haven't really made any money until "the money leaves the stock market and gets into your bank account."
"I think that sometimes we forget why we own stocks. We own stocks to create wealth," said Cramer, who contended there also is not a compelling reason to deploy profits back into stocks that have lagged during the broad rally.
"There's no sense for a lot of our investors who watch to rotate into something that hasn't moved when they can just sit and wait with some cash," he said. "Cash has been so vilified."
In addition to the risks presented by the coronavirus, Cramer also pointed to the recent spate of general election polls that show presumptive Democratic nominee Joe Biden with a sizable lead over President Donald Trump.
"[Biden] says the corporate tax rate should go up. That's $20 off the S&P," Cramer estimated.